William Hague today warned the new parliamentary watchdog not to try to re-write plans to clean-up the system of MPs expenses.
The shadow foreign secretary became the most senior politician to speak out after Professor Sir Ian Kennedy let it be known that he was thinking of dropping key elements of the blueprint for reform.
The plan, published last week, was drawn up by Sir Christopher Kelly, the chairman of the Committee for Standards in Public Life, after an extensive consultation.
However Sir Ian, the £100,000-a-year, three-day-a-week head of the new Independent Parliamentary Standards Authority (Ipsa), has made clear he has no obligation to accept Sir Christopher's recommendations and is planning to run his own consultation.
In particular he was said to be preparing to drop plans to require MPs to hand back any profits they make on the sale of homes bought with mortgages subsidised by the taxpayer and the ban on MPs employing family members.
However, Mr Hague warned that it would to nothing to restore public confidence if Sir Ian tried to reopen the matter now.
"I think it would be wrong to re-write what has now been produced," he told BBC1's The Andrew Marr Show.
"The public are pleased with what Sir Christopher Kelly has said and we have to accept it, not quibble about it, and we don't really want somebody else to come in and quibble about it either.
"That would be unwise and unnecessary."