by political editor Paul Francis

The Prime Minister has called for a shake-up in the benefits system to end what he labelled a "culture of entitlement" that had evolved over many years.

Mr Cameron said a debate was needed on welfare and outlined some options for consideration during a set-piece speech to Conservative party activists at the Bluewater shopping centre in Dartford today.

He said a welfare gap had developed that meant one in six children in the UK were brought up in workless households - the highest in Europe.

It was time to reform a benefits system further to create a situation where it did not pay to be out of work.

Among suggestions were cutting housing benefit for the under-25s and setting benefits at a lower level for those under 21.

"I don't deny that these are big, tough questions. But when you have got 300,000 children living in households where no one has ever worked, then you cannot shy away from them any longer."

In his speech, Mr Cameron said taxpayers were resentful about a system of working-age benefits that had gone "truly awry" and created a "welfare gap between those living long-term in the welfare system and those outside it".

He went on: ""If it is a real safety net, then clearly it's principally for people who have no other means of support, or who have fallen on hard times. But there are many receiving today who do not necessarily fall into these camps.

For example, the state spends almost £2billion a year on housing benefit for under-25s.There are currently 210,000 people aged 16-24 who are social housing tenants.Some of these young people will genuinely have nowhere else to live - but many will."

Mr Cameron has come under fire for some of his suggestions, with charities saying they risk making more young people homeless.

Some have seen it as an attempt to win over some within his own party who are unhappy about his brand of "compassionate Conservatism."

The PM said he was not turning his back on the vulnerable.

"Compassion isn't measured out in benefit cheques - it's in the chances you give people - the chance to get a job, to get on, to get that sense of achievement that only comes from doing a hard day's work for a proper day's pay. That's what our reforms are all about."