Media playback is unsupported on your device Media caption The first PMQs question to George Osborne is a challenge over house building and housing benefit in London

Chancellor George Osborne has taken centre stage for the first time at Prime Minister's Questions where he stood in for David Cameron.

Mr Osborne has spent 10 years beside Mr Cameron at parliament's showpiece occasion, first on the opposition benches and since 2010 in government.

He fielded 30 minutes of questions from MPs.

Hilary Benn - also making his first appearance at the event - asked the questions for Labour.

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It was the first time Mr Osborne has deputised for Mr Cameron, who is continuing his European tour to lobby leaders over EU reform ahead of the upcoming in/out referendum in the UK.

He was loudly cheered by Conservative MPs as he got to his feet at the despatch box.

But MPs sat in silence - an unusual event for Prime Minister's Questions - as Mr Benn, the shadow foreign secretary, asked Mr Osborne about the steps being taken to prevent young people joining ISIS and to deal with refugees in the Mediterranean.

War zones

The two men welcomed each other to their new roles, with Mr Osborne saying he was sure Mr Benn's father Tony would have been "proud" of him, although he could not resist a jibe at left wingers in the Labour leadership contest, saying there are "no Benns in the leadership contest but plenty of Bennites".

Mr Osborne said Britain will continue to play its role in humanitarian rescues of people trying to flee across the Mediterranean when HMS Bulwark ends its deployment.

He said it was vital to break the link between people trying to escape war zones by travelling across the seas and winning asylum having been rescued from the water or entering Europe illegally.

The SNP's leader at Westminster, Angus Robertson, asked if the Chilcot Inquiry into the Iraq war would be now be published next year. Mr Osborne said it was an independent process but patience was running out.

During the coalition years, Liberal Democrat Deputy Prime Minister Nick Clegg would stand in for the PM when he was away, with former First Secretary of State William Hague stepping up when they were both absent.

Mr Osborne, who was made deputy prime minister in all but name after the election, has been tipped as Mr Cameron's successor, after the prime minister announced that he would not seek a third term in 2020.

Mr Cameron also named Home Secretary Theresa May and London Mayor Boris Johnson, now a Conservative MP, as potential future leaders.

What is prime minister's questions?

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Each week on Wednesday afternoon the prime minister must come to the House of Commons to answer questions from backbench MPs and opposition leaders for half an hour.

This system was changed by Tony Blair's Labour government shortly after they came to power in May 1997. Previously PMQs took place on Tuesday and Thursday afternoons for 15 minutes.

Prime minister's questions follows a different format to those of questions to other ministers. MPs do not normally give the prime minister prior notice of the subject which they are going to raise.

This element of surprise allows opposition MPs, in particular, to try to catch the prime minister out with an awkward question. although they are not allowed to ask follow-up questions which limits their scrutinising powers.

Government backbenchers can normally be relied upon to ask a "helpful" question which will allow the prime minister to tell the House about successful government policies.

The relative performance of each of the main party leaders is closely watched and each is under great pressure to get the better of their opponent.

The names of the MPs who will get the chance to ask the prime minister a question are drawn in a weekly lottery.

Mr Osborne has been accused by Labour of prioritising his "personal ambitions" over his day job as he prepares for PMQs, after the chancellor said he would not be responding to an opposition debate on productivity, taking place immediately after.

Shadow chancellor Chris Leslie said he was "very surprised" he would not be in the debate and suggested Mr Osborne should "rein in your own personal ambitions", during Treasury questions on Tuesday.

Responding, Mr Osborne said: "I never thought I'd say 'bring back Ed Balls'", before joking that Labour needed to work on the "productivity of its own front bench".