In his last public statement before his retirement in July, cabinet secretary Sir Richard Wilson has backed proposals for a civil service act to police "spin doctors".

Political advisors, he said, should be split between those that brief the media and those that are hired for their specialist skills in that area and have no contact with journalists.

In a speech to senior civil servants, the civil service chief, whose replacement is due to be announced in the next two weeks, called for a limit on the number of advisors to two per department, in addition to those based at Downing Street.

Civil service commissioners should ensure the impartiality of the civil service, while special rules should be devised to govern spin doctors such as Jo Moore, formally in the department of transport, the mandarin said.

Wilson also discussed outside advisors, such as Number 10 transport advisor and former BBC director-general Lord Birt.

Shadow cabinet office minister Tim Collins welcomed the speech, and gave his party's backing to the legislation.

"It is sad that Labour have diminished standards in government so far that a new piece of legislation is necessary, but they have broken so many conventions that we must act now to protect the independence of the civil service," he said."Labour need to fundamentally rethink the way they run government. The prime minister must lead from the front, which means he should recommit himself to sacking Ministers who lie and to putting a stop to the constant attacks on civil servants by some of his senior ministers. He should also act to put the ministerial code into law, since he has so utterly failed to enforce its provisions when he should have".Deputy leader of the Liberal Democrats and cabinet office spokesman, Alan Beith, said he looked forward to Wilson's contribution, but warned against the government moving way from the debate.

"This should not let the prime minister off the hook. He should be taking the lead on this issue," he said.

"All too often, it has been advisers claiming to be acting on the prime minister's behalf that have been undermining the independence of the civil service.

"As the Minister is ultimately responsible for the civil service, the prime minister should be part of the solution, not part of the problem."