The Prime Minister has tweeted that the Chancellor has just briefed the Cabinet on the Spending Round, which he will announce publicly later today.
The head of the Institute for Fiscal Studies, Paul Johnson, has said there is "a good chance" the next government will raise taxes rather than pushing ahead with cuts.
"The scale of the cuts are really astonishing," Mr Johnson said. "If you really do carry on with the next two years up to 2017-18 as pencilled in that will result in a whole slew of government spending one third or more less than it was in 2010.
"So, if I was a betting man I would think there would be some kind of tax rises after the election."
Labour leader Ed Miliband has accused the Chancellor of breaking his promise to taxpayers by perpetuating austerity well beyond the next election - longer than initially planned.
George Osborne will today announce cuts worth £11.5 billion to public spending in a bid to reduce the government deficit.
But Mr Miliband also denied accusations of hypocrisy for criticising the Spending Review when he has admitted that Labour would not be able to reverse the cuts: