Deputy Director of the Institute for Fiscal Studies (IFS) Carl Emmerson said that since the last Budget, the UK's economic outlook has "deteriorated" and Government receipts have "disappointed".
Mr Emmerson suggests that as a result, Chancellor George Osborne might find himself having to "abandon" one of his fiscal targets.
If much of the additional weakness this year feeds into a permanently higher outlook for borrowing, then in order to comply with his other fiscal target Mr Osborne would need to announce yet more tax rises or spending cuts for the next parliament in next week's Autumn Statement.
In that case the planned era of austerity could run for eight years - from 2010/11 to 2017/18.
More top news
If Number 10 announces it plans to hold a vote on airstrikes in Syria, the planners in the MoD might as well get to work straight away.
Britain should not "sub-contract its security to other countries" while terrorists plan attacks from Syria, David Cameron will warn MPs.
The number of children dying from cancer in the UK each year is falling, according to new figures from a major charity.