The cabinet under David Cameron will feature five Liberal Democrats including Nick Clegg

David Cameron is preparing for his first cabinet meeting as prime minister as he puts the finishing touches to his historic coalition government.

The Tory leader will announce a string of junior government posts, which will include further Lib Dem appointments.

He began the business of government on Wednesday evening with a first meeting of the new National Security Council.

It followed a press conference in the No 10 garden with deputy prime minister and coalition partner Nick Clegg.

The two men joked together as they set out what they wanted to achieve with their unprecedented power sharing arrangement - which Mr Cameron said could mark a "seismic shift" in British politics.

In addition to Mr Clegg, four other Lib Dems will be sitting around the cabinet table when the ministers gather at 0900 BST.

They are Vince Cable, who is business secretary; Chief Secretary to the Treasury David Laws; Energy and Climate Change Secretary Chris Huhne; and Scottish Secretary Danny Alexander.

ID cards

There are expected to be 20 Liberal Democrat ministers at all levels across many departments, meaning nearly half of the parliamentary party will be members of the government.

The majority of cabinet ministers carry on with the briefs they held in opposition but there was a return to frontline politics for former Tory leader Iain Duncan Smith, who becomes work and pensions secretary.

Theresa May was a surprise appointment as home secretary and she has already spoken of the challenges ahead as she tries to square the conflicting priorities of the coalition partners and deliver their jointly agreed programme.

She told BBC News: "We will be scrapping ID cards but also introducing an annual cap on the number of migrants coming into the UK from outside the European union."

She said there was a "process to be gone through" to decide the annual limit. The coalition government was committed to introducing elected police commissioners and cutting police paperwork to "give the police more time on the streets," she added.

On the DNA database, she said: "We are absolutely clear we need to make some changes in relation to the DNA database. For example one of the first things we will do is to ensure that all the people who have actually been convicted of a crime and are not present on it are actually on the DNA database.

"The last government did not do that. It focused on retaining the DNA data of people who were innocent. Let's actually make sure that those who have been found guilty are actually on that database."

National Security

One junior government post was revealed on Wednesday evening, when Dame Pauline Neville-Jones took her seat as security minister at the first meeting of the National Security Council.

The body, made up of senior ministers, military chiefs and the heads of the security services, discussed the military situation in Afghanistan.

It was also briefed on the UK's wider strategic and security position.

Deputy Prime Minister Nick Clegg, Chancellor George Osborne and Foreign Secretary William Hague were among those who attended the Downing Street meeting.

The council was set up on Wednesday to co-ordinate the efforts of government departments and agencies to safeguard UK security.

A Downing Street spokesman said: "The prime minister this evening chaired the first meeting of the newly established National Security Council.

"The prime minister began the meeting by paying a full tribute to the UK's armed forces and expressed his personal admiration and gratitude for their dedication and sacrifice.

"He then received briefings on the political and military situation in Afghanistan, including from his new National Security Adviser, Sir Peter Ricketts, and from the Chief of the Defence Staff [Sir Jock Stirrup]. The prime minister was then updated on the wider UK security situation."

The Labour Party has meanwhile started the process of choosing a new leader after the resignation of Gordon Brown, who stood down as prime minster on Tuesday when it became clear that the Lib Dems had decided to join the Tories in a coalition.

Former Foreign Secretary David Miliband became the first potential candidate to announce plans to stand, saying he hoped others would follow suit. He has the backing of heavyweight figures including former home secretary Alan Johnson and acting Labour leader Harriet Harman, both of whom have ruled themselves out of the running.

Backbench Labour MP John Cruddas, who came third in Labour's 2007 deputy leadership contest, has also said he is thinking about standing.