A Tory backbencher has hit out at "jobs for the boys" in government after David Cameron drafted in Jo Johnson to head his policy unit.

Adam Afriyie said there were too many ministers, and new posts were being created apparently to alleviate political pressures.

The Prime Minister appointed Orpington MP Mr Johnson – London Mayor Boris Johnson's brother – as a Cabinet Office minister last week, giving him a key post overseeing policy. Labour has accused Mr Cameron of trying to buy loyalty in the Conservative ranks by handing out official roles.

In an article for the ConservativeHome.com website, Mr Afriyie – rumoured to be positioning himself as a future party leader – wrote: "In our 2010 manifesto we were committed to reducing the size of government.

"And yet, three years on, it only seems to be growing in size and expanding in reach.

"To me, this expansion is deeply worrying and rather perplexing."

He complained there were currently 31 people attending Cabinet on a regular basis, far more than on the boards of even the largest private companies.

"The overall number of ministers has risen from around 80 in 1950 to around 120.

"Basically, there are just too many government departments, and there are too many people attending Cabinet to make it an effective decision-making body," he wrote.