Sir Christopher Kelly, the chair of the Committee on Standards in Public Life, has been urged to undertake an investigation into the jobs taken up by former ministers and senior civil servants.
He spoke during an evidence session by the Commons Public Administration Committee on 6 March 2012 on the so-called 'business appointment rules'.
They are overseen by the Advisory Committee on Business Appointments (Acoba), which gives advice on possible conflicts of interest.
Labour MP Paul Flynn described Acoba as "a Bagpuss with no teeth or claws", and questioned whether the whole system needed to be reformed.
Meanwhile Conservative Charlie Elphicke said Sir Christopher's committee was not doing enough to tackle perceptions of a "revolving door" between Whitehall and private companies.
Sir Christopher admitted there were questions as to whether Acoba had sufficient resources to carry out its work properly.
The committee also heard from Chandrashekhar Krishnan from Transparency International UK and Professor David Miller from campaign group Spinwatch.
Professor Miller said there needed to be a wider definition of lobbying.
He said that people could engage in lobbying without simply taking part in face to face meetings.