By Dominic Casciani
BBC News community affairs reporter
Michael Howard: Firm or xenophobic?
Does Britain have an immigration problem?
Conservative leader Michael Howard certainly thinks we have - in January his party paid for a full-page advertisement in the Sunday Telegraph to tell us so. And he is determined to keep it high on the pre-election agenda, clearly convinced that it has resonance with voters.
Labour knows it is battling on credibility, whether or not it is the author of its own misfortune. Its "five-year plan" aims very much to reassure but also appear tough.
The Tories want to appear "tougher" - but do they risk being labelled xenophobic if they do so?
Michael Howard thinks he has the answer with quotas and, his latest idea, HIV and TB testing for some potential migrants.
Work permits will be granted as they are in Australia where potential immigrants get points relating to skills. The more demand for their skills, the more likelihood of being allowed in. Parliament will set an annual limit to the actual numbers allowed in.
On asylum, however, nobody will be allowed in at the borders. Those seeking protection will be held in overseas centres and have their cases assessed by the United Nations. Genuine refugees will then be allowed in, subject to an upper limit.
Mr Howard says these measures and others will deal with what he says are fears that communities "can no longer absorb newcomers at today's pace".
The health proposals are not new - the ideas have been floating around for some time - but there are questions about how they would work in practice. The government insists TB screening already takes place, because it can be contagious, but has not embarked on testing for HIV.
The Conservatives say they would screen people coming to work or settle, but not other categories of migrants.
To use 2003 migration figures as an example, some 8,200 African workers may have faced health checks prior to arrival - but not the 600,000 others who came as tourists or business people.
Quotas for work, are not unusual. The US has its annual "green card" lottery for 50,000 economic immigrants.
Here, the Home Office sets figures for some of the work permit schemes such as the catering industry.
But if immigration is driven by employers seeking workers and workers seeking a better life, then would a fixed limit be responsive?
What would happen if a successful business cannot expand because it can neither recruit locally nor bring in a suitably qualified foreign worker because the quota is full?
Would a limit discourage or encourage the disappointed would-be migrant from seeking less legal routes to working in the UK?
This is the dilemma at the heart of immigration economics.
The public want to see a system "under control", but employers and some economists demand flexibility.
Contributing to the fog are mixed media messages about migrant motives and disagreement over what happens if you put controls in place, or take them away.
The proposals on asylum will also face similar levels of scrutiny. Mr Howard says a Conservative government would pull out of the UN Convention on Refugees - the key agreement which allows people to claim refuge from persecution.
At the same time, it suggests the UN should run the proposed camps allowing access to the UK.
Refugee agencies predict disaster: the international agreements on refugees would collapse, potentially leading to more chaos and possibly creating more immigration to the industrialised world.
Secondly, what would happen if the asylum quota was full yet there were still people whose lives were at risk? Would the UK leave them to their fate?
The Tories say this is a nonsense argument from the refugee agencies because it envisages a system where the UN itself will select genuine refugees to come to the UK.
However, the UN has roundly condemned the policy. It is worth noting that the government is trying this type of approved refugee scheme already and has so far found only two areas willing to take newcomers.
But one of the key unanswered questions is what exactly does Michael Howard mean when he says communities can no longer absorb immigration at today's pace.
Although net immigration has steadily risen to about 150,000 in 2003, it is dominated by those who hold work permits.
Asylum is now much lower than it has been for some time. In 2003 it fell by 41% to about 49,000 applicants.
Trevor Phillips, chairman of the Commission for Racial Equality (and a former Labour party member of the London Assembly) argues that given a large number of those arriving are from inside the EU, the United States, Australia and New Zealand, then any immigration clamp-down would need to start there.
If not, he suggests, then Mr Howard has given enough space to racists to present Conservative policy as wanting to keep out people with dark skins. Michael Howard says that it is a "disgraceful allegation".
With politicians jockeying for position - Labour is expected to reveal its proposals soon - the coming months will show whether a national debate on immigration will be one based on what we know, or more on what we fear.