The government faces a multibillion-pound bill to close up to 180 quangos and in some cases it could be a decade before any savings are felt, according to documents that show the scale of the struggle the Treasury is facing to cut the deficit.

The Cabinet Office is poised to publish a list of the organisations facing closure or merger in its "bonfire of the quangos" next week. But private papers reveal that in several cases the liabilities from pensions, redundancies and rental contracts could outweigh any of the savings being claimed for up to 10 years.

There are concerns within the government that quangos are not producing the immediate savings the coalition had hoped for to help obliterate the £153bn deficit by 2015, adding to the intense pressure on the chancellor, George Osborne, to find every penny to meet the target.

Osborne also came under pressure yesterday to extend the five-year deadline to tackle the deficit. The Scottish parliament, the Welsh assembly and the Northern Ireland assembly issued a statement urging a scaling back of the plans, warning that the economic recovery was becoming endangered by the cuts.

The statement came as more details of the job cuts within Whitehall emerged, with departments told to make up to a third of their employees redundant. The education department is understood to be looking for a 30% reduction in staff. In the Department for Culture, Media and Sport the 50 top civil servants were told last week to reapply for just nine jobs that will remain.