Ken Clarke has made his first appearance on the Conservative frontbench for over six years.

The former chancellor was speaking for the Opposition in a Commons debate on the failure of the government to introduce a civil service bill.

Although not in the Shadow Cabinet, the Rushcliffe MP has been invited by Michael Howard to sit on an advisory council of "wise men" and make occasional contributions from the Despatch Box.

Clarke opened by saying what "pleasure it is to be making a guest appearance at the Despatch Box which I have encountered in the past". "It is indeed a pleasure, it is always an honour to represent one's party on the frontbench," he added.

"I am grateful to my old friend, the leader of the Opposition, to speak from the frontbench on this particular subject."

During the debate, Clarke, who also held Cabinet posts at health, education and the Home Office, called for urgent introduction of legislation to define the relationship between ministers, special advisers and mandarins.

Calls for a bill have become louder following the growth in the number of special advisers under Labour and Lord Hutton's inquiry which investigated the role of former Downing Street communications chief Alastair Campbell.

Despite promising to do so, the government has not found time to introduce legislation on the subject although the public administration select committee has published a draft bill.

"The government's abuse and politicisation of civil servants has helped to feed the growing public cynicism about politics and public life," Clarke said.

"The government has always said that it supports the case for defending the political impartiality of the civil service and the need to implement it."The case for a civil service bill has never been stronger and it is lamentable that the government has failed to carry out its seven year promise to enact one.

"The evidence to the Hutton inquiry shows how urgent it is that we legislate to defend the integrity of public servants without further delay."

In response Cabinet Office minister Douglas Alexander welcomed Clarke's return to frontline politics.

But he noted the "Conservative government's failure to legislate on the civil service".

And he promised that the government would "publish a drat bill in the current session of parliament".