By Brian Wheeler
Political reporter, BBC News
Cash-for-influence allegations against four Labour peers have once again thrust the murky world of political lobbying into the spotlight.
The peers have denied any wrongdoing
The four have denied any wrongdoing but Gordon Brown has promised "emergency sanctions" against them if allegations they offered to help make amendments to legislation for cash are proved.
The idea of politicians offering to change the law of the land in exchange for a fat fee is regarded with genuine dismay by the average MP or peer, most of whom insist British politics is relatively free of financial corruption.
Yet for some the current scandal is a wake-up call for Britain's political classes and it has led to renewed calls for reform of the lobbying system.
One of Barack Obama's first acts as US President was to clamp down on lobbying and, in particular, the "revolving door" which sees members of an administration walk straight into highly paid jobs with the companies or industries they had jurisdiction over. Gifts from lobbyists were also banned.
There is a growing body of opinion across all parties that something similar is needed in the UK.
No one is seriously suggesting an outright ban on lobbyists. They are a fact of life in most democracies.
Banning them would probably drive the practice further underground - and result in more meetings by the lake at St James' Park with dark glasses and a rolled-up newspaper, as the CBI's John Cridland put it to MPs last year.
Politicians cannot make laws in a vacuum. They need to speak regularly to industry, trade unions and campaign groups to formulate effective policy.
Imagine the outcry if MPs refused to meet a delegation of small business people or environmental campaigners.
Because secret lobbying by its very nature leaves no evidence trail, there could still be a significant problem even with little concrete evidence of one
Public administration select committee
But the problem, according to a report by the Commons public administration committee, is that lobbying in the UK can be a secretive business, that deals are "traditionally done behind closed doors".
They also highlight the fact that former ministers are allowed to take lobbying jobs while they continue to sit in Parliament.
We know, from the register of members' interests, that many backbench MPs and peers, from all parties, are on the payroll of companies, either as directors or consultants.
The companies involved range from small, obscure specialists in surveillance, security, financial services, law and dozens of other areas to some of the biggest names in British industry, such as defence giant BAE Systems or retailer Boots.
The nuclear industry has been particularly active in recruiting senior Labour politicians and former members of the government.
We also have an idea of the sort of money they get.
Among former ministers who continue to sit in the Commons, Alan Milburn earns £30,000 a year from Pepsico, Patricia Hewitt gets £50,000 a year from Boots and David Blunkett supplements his backbenchers' salary of £63,000 a year by as much as £135,000 with various directorships and consultancies.
Peers are less forthcoming. Nine of them declare how much money they are receiving in their roles as parliamentary consultants for companies.
But many more, as many as one in five, list their jobs as non-Parliamentary consultant, which means they do not have to declare how much they receive. They must declare an interest when they speak on matters relating to the company, but they can still vote on legislation which may affect its business.
And there are press reports that some have set up private companies to enable them to carry out consultancy work without revealing the identity of their clients.
Barack Obama has announced a crackdown on lobbying
There are well-established rules governing what MPs and peers employed as consultants can and cannot do.
They are not allowed to table amendments or vote on bills in exchange for payment. Former ministers are normally banned for at least 12 months from becoming lobbyists in their specialist fields.
But what we do not know - what nobody really knows - is how much influence lobbyists actually have on legislation. What do companies get for their money?
Because their meetings with ministers and civil servants go on behind closed doors and minutes are not published, it is difficult to tell.
Before the current scandal broke, the government said there was little evidence of problems in the UK lobbying system.
But the public administration committee argued in its report that "because secret lobbying by its very nature leaves no evidence trail, there could still be a significant problem even with little concrete evidence of one".
In private, lobbying consultants and PR companies may talk up the influence of their tame MPs to impress corporate clients.
The politicians themselves may also try to create the impression that they have the ear of a minister, or even the prime minister. Some of them might even believe it.
Then again, some talk down their influence or suggest that they have not been employed for their past experience as a member of the government at all.
Former sports minister Richard Caborn, who last year received between £70,001 and £75,000 from construction giant and nuclear contractor AMEC, denies his consultancy work has anything to do with his former government job.
"It is not about lobbying at all; it is about the fact that I am an engineer and I have had a lot of experience in Europe and have been a trade union official. It is nothing to do with my ministerial career," he told the public administration committee.
Former Labour chairman Ian McCartney, who receives between £110,000 and £115,000 as a senior adviser to nuclear power giant Fluor Corporation, although he does not take this money as personal income, told the committee: "I don't lobby for Fluor and this is explicit in our agreement, lodged with the House authorities."
Both men were cleared to take on the consultancy work by the House authorities and there is no suggestion they have done anything wrong under the current rules.
But the public administration committee came to the conclusion that their corporate paymasters were probably more interested in their address books than their knowledge of Parliamentary procedure.
"It stretches the bounds of credulity to suggest that the fact that they were former ministers with contacts in government did not play a part in the decisions by AMEC and Fluor to employ them," the report says.
"Part of the appeal of employing former ministers is the perception - accurate or not - that they will be able to offer access across government. This is particularly so when the their party remains in government".
It called for a tightening up of the rules to prevent former ministers being able to "use with impunity the contacts they build up as public servants to further a private interest".
Sheila Krumholz, of the US centre for responsive politics, expressed astonishment this week that British lawmakers were being paid by companies to act as consultants at all.
It would not happen in America, she told lobbying transparency campaigners at a meeting in the Commons.
Lobbying is arguably a more powerful, and certainly better funded, force in US politics than it is in the UK but it is also more out in the open.
The centre's Open Secrets website includes a searchable database of campaign funds and individual lobbyists, detailing their links with politicians and industry.
Ms Krumholz suggested Britain could learn from the US, but added: "The UK has the opportunity to create the world's most transparent system for tracking lobbying of the government, starting basically from scratch, which is a huge advantage."
She said the register should include expenditures per lobbying client relationship, list lobbyist's names, their former official positions, CVs and political connections, allowing voters to track the "revolving door".
Campaigners in the UK want to go even further and publish minutes of meetings between lobbyists and ministers and name the actual civil servants that are being lobbied.
But the public relations industry has warned against an over-reaction to the current crop of lurid headlines, stressing that nothing has been proved against the four Labour peers.
Lionel Zetter, former chairman of the chartered institute of public relations, argues it is "impractical" for lobbyists to record every meeting with civil servants and MPs. He also scoffs at the idea that the industry is shrouded in secrecy, particularly since the advent of the Freedom of Information Act.
"There is no question of secrecy. You can not approach a minister or a civil servant and say 'I am not going to tell you who I am working for'," says Mr Zetter, author of a book entitled Lobbying: The Art of Political Persuasion.
Democracy could not function properly without lobbying, he argues, and it is always the "coherence" of the lobbyists' arguments, rather than the depth of their pockets, that wins the day.
He also firmly rejects claims by the public administration committee that the lobbying industry is "scarcely regulated at all".
There are three trade bodies, including the Association of Professional Political Consultants which has a code of conduct banning members from employing elected politicians or peers and strict rules on honesty and openness, keeping tabs on the activities of lobbyists.
But he concedes that lobbyists do not have to join a trade body and sign up to their rules if they choose not to, and that there might be a case for a compulsory lobbying register.
He also stresses that the industry has not rejected the findings of the select committee entirely and is still considering its response to their report.
"We are not stupid, we know there is a problem. It is a problem of perception as much as anything, but there is a problem," he adds.
Before the current scandal broke, Cabinet Office minister Tom Watson told the public administration committee: "If in the course of your investigation, you have found a systemic problem with the lobbying industry I would like to see it but my impression is we have a pretty good system in the UK."
Whether the ongoing investigation into the alleged activities of the four Labour peers leads Mr Watson, or other ministers, to revise this assessment and introduce the reforms campaigners are demanding remains to be seen.