David Cameron is UK's new prime minister

Conservative leader David Cameron has become the UK's new prime minister after the resignation of Gordon Brown.

Lib Dem leader Nick Clegg will be his deputy after they agreed to the UK's first coalition government in 70 years.

Mr Cameron, who at 43 is the youngest PM in nearly 200 years, vowed to set aside party differences and govern "in the national interest".

Mr Clegg said he acknowledged some Lib Dem voters would have doubts about the deal but urged them to "keep faith".

Mr Cameron's party won the most seats in the general election last week, but not enough to secure an overall Commons majority, resulting in a hung Parliament.

'Unique opportunity'

Following hours of talks with the Conservatives on Tuesday, the Lib Dem parliamentary party and its federal executive endorsed the coalition agreement by the required three-quarters majority at a meeting that broke up just after midnight.

Speaking minutes later, Mr Clegg said: "I hope this is the start of the new politics I have always believed in - diverse, plural, where politicians of different persuasions come together, overcome their differences in order to deliver good government for the sake of the whole country."

He acknowledged there would be problems and "glitches" and, in a message to Lib Dem voters, he added: "I can imagine this evening you'll be having many questions, maybe many doubts, about this new governing arrangement.

"But I want to assure you that I wouldn't have entered into this agreement unless I was genuinely convinced that it offers a unique opportunity to deliver the kind of changes you and I believe in.

"So I hope you'll keep faith with us, I hope you will let us prove to you that we can serve you and this country with humility, with fairness at the heart of everything we do, and with total dedication to the interests and livelihoods of everyone in Great Britain."

Meanwhile, details are emerging from Conservative sources about the new government's programme, including:

Plans for five-year, fixed-term parliaments
The Lib Dems have agreed to drop plans for a "mansion tax", while the Conservatives have ditched their pledge to raise the inheritance tax threshold to £1m
The new administration will scrap Labour's planned rise in National Insurance but some of the benefits will go on reducing income tax thresholds for lower earners
A pledge to have a referendum on any further transfer of powers to the EU and a commitment from the Lib Dems not to adopt the euro for the lifetime of the next Parliament
The Lib Dems have agreed to Tory proposals for a cap on non-EU migration
The Conservatives will recognise marriage in the tax system - Lib Dems will abstain in Commons vote
The Lib Dems will drop opposition to replacement for Britain's Trident nuclear missiles but the programme will be scrutinised for value for money
There will be a "significant acceleration" of efforts to reduce the budget deficit - including £6bn of spending reductions this year
There will be a referendum on moving to the Alternative Vote system and enhanced "pupil premium" for deprived children as Lib Dems demanded
Mr Cameron has begun the work of appointing his first cabinet, with the Tories' George Osborne as chancellor, William Hague as foreign secretary and Liam Fox as defence secretary.

Mr Clegg's chief of staff, Danny Alexander, who was part of the party's negotiating team, is to be Scottish Secretary, the BBC understands.

Lib Dem Treasury spokesman Vince Cable has been given responsibility for "business and banks" but it is not known if his title will be chief secretary to the Treasury, a senior Lib Dem source said.

A Downing Street spokesman said it had been agreed that five cabinet posts would be filled by Liberal Democrats, including the appointment of Mr Clegg, although there are expected to be about 20 Lib Dems in government jobs in total.