Mr Cameron, at 39, faces Tony Blair across the dispatch box at Question Time today after becoming the 26th leader of the Conservative Party. He scored a decisive victory over David Davis, beating the Shadow Home Secretary by more than two to one, gathering 134,446 votes to 64,398.

And, in a swift illustration of his determination to reclaim the centre ground for the Conservatives, he broke with the legacy of Thatcherism, declaring that there was such a thing as society, and promised a new style of politics that would mean the Tories backing the Government if they thought it was right for the country.

He told his party to stop grumbling and to accept modern Britain as it was.

With the authority of his massive victory behind him, Mr Cameron prepared to lay down the law to MPs, saying that he wanted an end to “Punch and Judy politics — the name-calling, backbiting, point scoring and finger pointing.”

His first test of that approach will come today when he becomes the fifth Tory leader to face Mr Blair. Last night he was in deep consultation with aides, debating whether to use today’s appearance to reflect a more consensual attitude or to attack Mr Blair over the Pre-Budget Report and Europe.

This afternoon he will travel to East London to deliver a speech in which he is expected to promise that, under the Tories, the voluntary sector would take over the current role of the public sector in tackling family breakdown, poor school standards, crime and rundown public spaces.

His “social action” plans have been chosen for his first policy announcement to show that the Tories are about to enter previous “no-go” territories. His next statement, on Friday, will be about the environment, a similarly unfashionable subject for the Conservatives in the past.

Mr Cameron will revealthe most senior members of his Shadow Cabinet today. George Osborne will be confirmed as the Shadow Chancellor. William Hague is expected to be Shadow Foreign Secretary and, The Times understands, Mr Davis is to remain in his post of Shadow Home Secretary.

Mr Cameron’s biggest personnel headache last night was the job for Liam Fox, the Shadow Foreign Secretary, who came third in the leadership race. Dr Fox could become the deputy leader, combining the role with another senior port-folio, such as defence.

There will also be senior roles for Oliver Letwin, Ther- esa May and Caroline Spelman. Mr Cameron may also give jobs to others who backed Mr Davis including David Willetts, Andrew MacKay, Julie Kirkbride and Andrew Mitchell. Edward Llewellyn is to become his chief of staff.

In a victory speech at the Royal Academy, Mr Cameron recalled saying as the campaign began that the party had to change. “Now that I’ve won, we will change. We will change the way we look. Nine out of ten Conservative MPs, like me, are white men.” He would change the “scandalous” under-representation of women.

He added: “We need to change the way we feel. No more grumbling about modern Britain. I love this country as it is, not as it was, and I believe our best days lie ahead.”

He showed he was ready to confront party critics who have opposed his decision to support the Government on occasions. “I want and I will lead a Conservative Party that, when the Government does the right thing, will work with them and, when they do the wrong thing, will call them to account.”

Mr Davis said that the election had shown the party as “democratic, intelligent, civilised, thoughtful and mature. A party of principles, a party of ideas. In short, a party fit for government.” He hailed Mr Cameron as “the next Conservative Prime Minister”.

More than 300,000 news- letters carrying Mr Cameron’s message of change were handed out at railway stations last night. Volunteers were pressing them into commuters’ hands in Leeds, Birmingham, Solihull, Bristol, Swindon, Manchester, Liverpool, Newcastle and Guildford as well as London.

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