They walked out after Sir Geoffrey Johnson Smith, the Tory chairman of the committee, used his casting vote to produce a report over the allegations that Neil Hamilton, a former minister, failed to declare hospitality at the Ritz in Paris.
Peter Griffiths, a Tory member of the committee, voted with Labour to tie the vote at 6-6. Labour MPs protested that the report was inadequate because the committee had interviewed only one witness, Peter Preston, editor-in-chief of the Guardian.
Bill Michie, one of the Labour members, said afterwards that Labour's protest had been aimed at "trying to get the committee to take witnesses other than Peter Preston". Other witnesses that Labour members sought included Mohamed al-Fayed, the owner of the Ritz Hotel and Harrods.
Another of the Labour MPs said: "We are just annoyed at the way this committee has been handled over the past five months. The walk-out was not planned. It was completely spontaneous."
The Labour MPs were also angry with the complaints made to the committee over an undeclared trip on Concorde to America by Tony Blair, their party leader.
But Conservative members said the walk-out had nothing to do with the allegations against Mr Blair, which are not being investigated.
Senior Tories strongly denied any suggestion of a cover-up by the committee. Sir Geoffrey, a senior member of the 1922 Committee of Tory MPs, said: "I am sorry the Labour MPs have walked out. I hope that they will return."
If the Labour MPs refuse to return to the committee, the six Tory MPs remaining will be faced with a dilemma over whether to continue with their inquiries into a range of complaints about alleged failures of ministers to declare their interests.
In a separate inquiry, the Commons privileges committee has called on Mr Preston to give evidence before it next month, before it decides whether to call other witnesses, including Mr Fayed.Reuse content