Public spending cuts will test the relationship between the devolved nations and the UK Government, according to a new report.
Prime Minister David Cameron's "respect agenda" sent out a reassuring message to Scotland, Wales and Northern Ireland but postponing funding cuts to these nations risks a backlash in England, the Institute of Public Policy Research (IPPR) report said.
However, the think tank argues that the devolution settlement can be strengthened despite difficult economic and political circumstances.
Alan Trench, a research fellow at Edinburgh University who contributed to the report, said: "Devolution has had an easy ride so far, with Labour dominating all three governments in Britain and generous public spending allocations.
"Now times are tough: not only is spending going to get very tight, but with different parties in office in Edinburgh, Cardiff and Belfast, party ties cannot help smooth intergovernmental relations in the way they did.
"That means that the UK Government needs to approach intergovernmental relations with great care to make the new system work. Complacency is not an option."
The Devolution In Practice 2010 report analyses how devolution has changed the UK since 1997.
IPPR associate director Guy Lodge said Mr Cameron "has gone out of his way in his early days in office to give a reassuring message to the people of Scotland, Wales and Northern Ireland through the 'respect' agenda".
However, he acknowledged that the Conservative mandate in Scotland, with just one MP north of the border, was "extremely weak". He said: "Grant funding to the devolved nations will have to be cut as part of the deficit reduction programme. Holding off cuts to the block grant until 2011-12 might help David Cameron to win friends in Scotland, Wales and Northern Ireland, but it risks a backlash from England - particularly those poorer areas which already look jealously at the funding those parts of the UK receive."
Public spending per head is higher in the devolved nations than in England, with spending more than £1,000 higher per head in Scotland and Northern Ireland than in England, and around £600 higher in Wales. The report recommends that the Barnett formula, which sets the funds Westminster gives to the devolved nations, be reformed so that it is fair to all parts of the UK.