David Cameron will signal today the end of "compassionate Conservatism" with plans for a crackdown on welfare spending for the young, the jobless and those with large families.

In a speech which will appeal to the Tory right, Mr Cameron will demand an end to what he calls Britain's "culture of entitlement". He will propose:

* Removing or restricting some benefits from out-of-work families with large numbers of children. This could include cuts to child benefit;

* Scrapping housing-benefit payments to 380,000 under-25s, worth an average of £90 a week, forcing them to support themselves or live with their parents and saving the Government £2 bn a year;

* Making the long-term unemployed carry out full-time community work or lose all their benefits.

Conservative sources suggested that some of the benefit changes could be brought in ahead of the next election.

However, this was disputed by the Liberal Democrats, who said that they would not allow measures penalising the vulnerable to pass during the lifetime of this Coalition Government.