The former Transport Secretary, Stephen Byers, has "a serious case" to answer following claims that he that he secured secret deals with ministers for firms, according to the shadow Commons leader Sir George Young.
His comments on the Today programme follow Mr Byers' claims to an undercover reported that he was "a cab for hire" who had engineered a deal with Transport Secretary Lord Adonis over the termination of a rail franchise contract, and that a similar intervention had got the Business Secretary Lord Mandelson to change regulations on food labelling.
Mr Byers has strongly denied the allegations, made by the Sunday Times and Channel 4 television.
Sir George said that the claims constituted "a clear breach of the rules" and that parliament had to "get a grip" on the matter.
But Education Minister Kevin Brennan said that while it was right that questions surrounding the allegations should be answered, he believed that Mr Byers alleged comments showed that he was "bigging himself up in order to try and win himself a job".
And he added: "The idea that Stephen Byers would be able to change government policy... is frankly ludicrous."