By politics.co.uk staff
Potential cuts to benefit payments for the over-65s have triggered a growing row within the coalition.
Iain Duncan Smith's Department of Work and Pensions (DWP), which clashed with No 10 repeatedly over the introduction of the universal credit, is once again at war with Downing Street over the future of benefits for old-age pensioners.
Mr Duncan Smith is thought to be looking at cutting the benefits bill by £5 billion through the cuts.
That is reportedly opposed by No 10 because David Cameron promised to protect payments for OAPs before the 2010 general election.
"The PM is refusing all logic on this because he has boxed himself into a political corner and doesn't have the courage to stand up to Labour’s attack," a source close to Mr Duncan Smith told the Sun newspaper.
"IDS' compromise, to start means-testing after the 2015 election will let him say he kept his promise in the parliament for which he made it."
Targeting rich elderly people for benefit payment cuts could make the move politically palatable. Winter fuel payments worth £200 are currently available for all those aged over 60, regardless of income, while those over 80 get £300 a year.
The prime minister faces further resistance to his refusal from his coalition partners, as deputy prime minister Nick Clegg has made clear he backs Mr Duncan Smith in the row.
His intervention signals that the Lib Dems are more willing to break their general election promise that winter fuel payments would be delayed until the age of 65, up from 60.
A party spokesman told the Guardian newspaper: "If you're faced with a choice in terms of helping the wealthiest pensioners or helping the vulnerable across Britain, then his priority is the vulnerable people across the country who need the most help."