GORDON Brown hinted he may scrap the £5bn identity card scheme as he launched the campaign that is expected to make him the next Prime Minister.

Speaking at a London gallery, the Chancellor ducked a challenge to give his full backing to the controversial project, which is expected to lead to compulsory cards for every citizen by 2012.

Instead, Mr Brown suggested he would set up an "independent review" and stressed the importance he attached to the "protection of civil liberties".

Earlier, Jack Straw, Mr Brown's campaign manager, also talked of an identity cards review, adding: "You build on the things which are successful and you have to change the things which are unsuccessful."

The evasiveness is certain to heighten speculation that the Chancellor is leaving the door open to abandoning the scheme, which has been dogged by mounting costs.

Over the past six months, the official bill for ID cards has soared by £840m to £5.75bn - although critics say the true cost could be four times as high.

Last month, it was revealed the Chancellor had refused to authorise the full budget for the scheme, only approving Home Office spending within "defined limits".

The campaign launch saw Mr Brown pledge repeatedly to "listen and learn" in the next seven weeks before he is expected to walk up Downing Street as prime minister.

He plans to meet "thousands of people" as he tours Britain to meet all sections of society - even if, as seems most likely, he faces no challenge to replace Tony Blair.

Mr Brown sought to reassure voters who fear a lurch to the left by stressing his commitment to reform of public services and that he was "one of the founders of New Labour".

He also promised to "restore the trust of the British people in our democracy".

Among the few new policies he hinted at were a written constitution and a beefed-up ministerial code, both designed to bolster the Government's accountability to Parliament and the public.

Education was his "passion", he said, but the financial turbulance in the NHS and the desperate need for more affordable housing would also be key priorities.

Mr Brown said: "In the weeks and months ahead, my task is to show I have the new ideas, the vision and the experience to earn the trust of the British people."

In a highly personal section of his speech, Mr Brown spoke of his "moral compass", the joys of fatherhood and a childhood accident on a rugby pitch that left him blind in one eye.

He rejected calls for a General Election when he takes over, adding: "I didn't hear the opposition saying in 1990, when Mrs Thatcher left, that there should be an immediate election".

However, the launch suffered an embarrassing hitch when Mr Brown's face was obscured by his glass autocue on live television coverage of his speech.

Earlier, Mr Blair - finally - endorsed his long-time rival to succeed him, insisting Mr Brown "has got what it takes to lead the Labour Party and indeed the country with distinction".

Darlington MP Alan Milburn also threw his weight behind Mr Brown, adding: "I do so in the hope and expectation that his leadership will rebuild the popular coalition of support that brought us three election victories."