Any tax cuts promised in ther run-up to the election will be reversed quickly by whoever wins, according to the Institute of Fiscal Studies.
Paul Johnson, a director at the IFS, said that if political parties looking to form the next government "are promising tax cuts, let's hear where the spending cuts will fall".
"It might be easy to announce immediate tax cuts, without any hint of what it is the state currently does that it will stop doing, or what taxes will rise in future, but this trade-off cannot be wished away.
“The post-election chancellor’s economic and fiscal inheritance will be miserable,” Johnson added.
Britain’s national debt is close to a peacetime peak at 97.7% of GDP and will be hard to reduce without a massive tax raise, suggested the IFS report.
“The challenge is that with higher levels of spending on debt interest, and forecasts suggesting that economic growth will continue to be weak, getting debt falling will be much more difficult than in the recent past – and arguably more difficult than at any point in the post-war period.”
Commitments on spending on the NHS, defence, childcare and international aid, will require £20bn to be found to avoid cuts to other services, the IFS said.
That is before the impact of an ageing population and climate change commitments start to be felt fully.
A Treasury spokesperson countered: "The best way to deliver sustainable funding for public services in the future is to grow the economy - the UK has grown faster than France, Germany and Japan since 2010 and the OBR say our action in spring and autumn will deliver the largest boost on record."
Chancellor Jeremy Hunt is expected to oversee an election hand-out Budget on March 6 with as much as £20bn in tax cuts and other fiscal measures.