George Osborne should introduce cash freezes to avoid missing his debt target, a right-wing think tank has said just days before the Autumn Statement.
The Centre for Policy Studies (CPS) claimed the country's debt will be between £20bn and £30bn higher than Government forecasts in 2015/16.
To avoid this, the organisation urged the Chancellor to save money by introducing freezes on international aid and all benefits except for the state pension.
The halt on public sector pay rises should also be clarified, it added, as "many departments have interpreted the existing freeze very differently".
These measures need to be part of a plan to reduce Government spending to 38% of GDP within four years, the CPS said, adding that a simplification of the UK's "dysfunctional tax system" is also needed.
The calls come ahead of the Autumn Statement on December 5, when Mr Osborne will reveal his latest economic plans to Parliament.
The CPS' head of economic research, Ryan Bourne, said it is clear that assumptions about the potential underlying growth of the economy have been over-optimistic.
"It's increasingly obvious that a further spending review is necessary, and this should go further in looking at the scope of government activity," he said.
And Tim Knox, the director of the CPS, stressed that need for a "great reduction in Government activity".
"The Chancellor has a choice: will he put the long-term economic health of the country above the temptations of short-term political gain?" he said.
"If he tweaks the numbers to meet his rules and if he announces a wide range of policy initiatives which might grab a few headlines, then we will know that this is a statement inspired more by politics than economics."
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