David Cameron is facing calls for an urgent rethink of government legislation aimed at preventing future lobbying scandals.
The chairman of the Commons committee which has been examining the Lobbying Bill has warned the plans lack credibility, dismissing them as a "dog's breakfast".
Labour MP Graham Allen, who heads the Political and Constitutional Reform Committee, said the bill would not open up the £2 billion lobbying industry to effective scrutiny.
"The new lobbying law is rushed and ridiculous," he told The Independent.
"Instead of addressing the Prime Minister's promise to 'shine the light of transparency' on lobbying, this flawed legislation will mean we'll all be back in a year facing another scandal. It is a dog's breakfast."
Mr Allen has taken the unusual step of recalling his committee during MPs' summer break for a series of special hearings to take further evidence from leading figures involved in the industry.
The bill is due to start its passage through Parliament when MPs return to Westminster, but Mr Allen is hoping the move will force ministers to rethink their plans.
It reflects concern that while the legislation would establish a statutory register of lobbyists, only firms which say it is their main business would need to register - excluding many key players.