The Liberal Democrats have demanded that the prime minister conducts an immediate reshuffle to fill the void left by Robin Cook.

MPs say Tony Blair must appoint a new leader of the Commons - more than a week after Cook's resignation and the biggest revolt ever on the government backbenches.

Paul Tyler, the Lib Dem Commons spokesman, said the failure to replace the Livingston MP was sending out the message that parliament is being sidelined.

"The prime minister must recognise that the House of Commons is not likely to take kindly to any attempt to browbeat MPs into submission," he told a conference organised by The House Magazine.

"Other controversial issues still concern MPs, such as foundation hospitals and student top up fees, and the only hope of survival for the government will be through sensitive management.

"Robin Cook believed that good government depends on good parliamentary scrutiny. His successor must share that commitment to parliamentary sovereignty and to cross-party cooperation, otherwise his whole programme of reform and modernisation could unravel."

He also warned the prime minister against appointing a Downing Street loyalist to the post.

"The names so far suggested as possible replacements for Robin Cook would be totally inadequate and unacceptable substitutes," said Tyler.

"In leaving the post vacant for so long speaks volumes for the importance Tony Blair attaches to parliament. Treating the House of Commons like an unimportant colony in need of a disciplinarian governor could prove fatal."

It has been speculated that Blair may appoint Hilary Armstrong - the current chief whip - to the post.

Such a move would be a clear sign that the role was being brought firmly back under the prime minister's control.

Ben Bradshaw, the deputy leader of the House, is currently acting as Commons leader.