Cameron hints at giving civil liberties role to 'big beast' David Davis - but won't have him in shadow Cabinet

The idea has been mooted by senior party figures and friends of Mr Davis said last night it made 'perfect sense'.

Mr Cameron has signalled that Mr Davis, who stood down as an MP to force a by-election in protest at Government plans to allow six-week detention without charge, cannot expect to return to his old job of shadow home secretary.

That position has now been filled by former shadow attorney general Dominic Grieve.

David Cameron (left) said he will campaign for the former Shadow Home Secretary David Davis

Mr Cameron made it clear yesterday that he disagreed with Mr Davis's decision to stand down.

'It's important that I have a team that is the top, permanent team ready to take over and ready to challenge the Government,' he said.

'There was an honest disagreement between me and David. He wanted to do this by-election and I didn't agree with it because I think the way we oppose the Government is in Parliament.'

Mr Cameron said, however, that he admired Mr Davis's 'courage'.

He is expected to travel to Mr Davis's East Yorkshire constituency of Haltemprice and Howden to campaign for him next week.

He held open the possibility of a senior post if Mr Davis was returned to Parliament in the poll on July 10.

'He's a big beast in the Tory jungle and he deserves to be a big part of the Conservative Party.'

Tory sources said one possibility was for Mr Davis to be made vice-chairman of the party in charge of a policy commission advising Mr Cameron on civil liberties.

A friend of Mr Davis said that although no discussions have yet taken place, he was open to the idea.

It emerged yesterday that Shami Chakrabarti is almost certain to appear on the campaign trail with Mr Davis.

Liberty, the campaign group she heads, usually avoids backing individual parties but may back Mr Davis because neither Labour nor the Lib-Dems are fielding a candidate.

Miss Chakrabarti has accepted an expression of 'regret' from Culture Secretary Andy Burnham over claims she had shared 'late night, handwringing, heart-melting' phone calls with Mr Davis.