Deputy Prime Minister Nick Clegg has dismissed reports that millions of pensioners and middle class families could see their benefits cut as "speculation".
Mr Clegg said it would be "irresponsible" to offer a running commentary about rumours of where spending will be cut.
The details will not be confirmed until October, he told Sky News.
"This is all speculation in the middle of August, when the comprehensive spending round hasn't even been decided yet," he added.
His remarks followed reports in the Daily Telegraph that ministers are looking to raise the age at which pensioners are eligible for the winter fuel allowance, from 60 years to 66.
Child benefit could also be scaled back, with reports suggesting parents in the top tax bracket could lose out.
A spokeswoman for the Department of Works and Pensions echoed Mr Clegg and said it was "not going to provide a running commentary" on what was being considered.
The Treasury also declined to comment on which payments could face the axe.
But a spokesman said the Government has made clear its "intention to look for further reforms" to the welfare system.
The Times also suggested winter fuel payments might be cut, as part of a £13bn reduction of the welfare bill to pay for changes proposed by Work and Pensions Secretary Iain Duncan Smith.
Winter fuel payments, introduced in the winter of 1997, cost about £2.7bn a year.
Prime Minister David Cameron pledged to keep the winter fuel allowance during the general election leaders' debates.
But the Liberal Democrats campaigned on a platform of reforming the payment by raising the age-related threshold to 65 to extend them for severely disabled people.
The coalition agreement pledges to "protect key benefits for older people such as the winter fuel payment", but does not rule out reform.
According to the Government's website Directgov, the qualifying age for winter fuel payments is already rising in line with the increase in women's state pension age - set to equalise at 65 by 2020.
Ministers have proposed speeding up plans to raise the state pension age for men to 66, possibly by as early as 2016.
Labour leadership candidate Ed Miliband said Mr Cameron should return from holiday to clear up the speculation.
It would be an "outrageous broken promise" if the Prime Minister axed benefits he had previously suggested he could keep, Mr Miliband told Sky News.