A Government-imposed gag on retired diplomats giving media interviews without prior approval is "oppressive" and must be scrapped, a Commons committee says today.

A Government-imposed gag on retired diplomats giving media interviews without prior approval is "oppressive" and must be scrapped, a Commons committee says today.

Tougher restrictions were written into diplomatic service contracts in 2006, sparking complaints from former mandarins that their free speech was being eroded.

The Public Administration Select Committee said rules were "excessively wide-ranging and oppressive" and would "substantially diminish informed discussion of major world events."

Their only saving grace is that they seem to be unworkable, they concluded, accusing ministers of failing to act on promises to revise them.

"Were the rules to be applied literally, they would prevent live TV or radio commentary from former diplomats for the rest of their lives.

"In practice, the Foreign Office continues to rely on the good sense of its former staff. It should say so. There is no sense in maintaining a rule that is both wrong in principle and manifestly unworkable in practice."

The government was also accused of "restricting free speech" by refusing to allow former civil servants to appeal against any decision to block publication of their memoirs.

The committee said that welcome moves to toughen the vetting process, in the wake of several highly- controversial books, had been undermined by the lack of an independent arbiter.

Passing Freedom of Information legislation meant the government had accepted it could not be the "ultimate arbiter" of whether information should be made public, the report said.

"It is indefensible to deny that principle in the specific circumstances of political memoirs," the MPs added.

Labour MP Tony Wright, who chairs the committee, said the government needed to go back to the drawing board. "The Foreign Office was clearly disturbed that former ambassadors like Christopher Meyer and Craig Murray were able to publish highly critical memoirs while paying only lip service to the rules," he said.

"But in trying to stop that happening again, they have changed the rules in a way that has - at least on paper - serious unintended consequences."