On the Today programme at 0750 this morning the business secretary Vince Cable was asked about suggested spending cuts of 35% to science spending. In a rare – and perhaps unplanned – exception to the rule of ministers not commenting on specific quanta of cuts ahead of October's spending review announcement, Cable rejected that figure explicitly saying "No, that's not right, that is way in excess of what we are talking about."

It is not clear where that 35% figure came from. William Cullerne Bown of the science periodical Research Fortnight mentioned it in his Guardian comment piece yesterday, but the only reference he gives is to an earlier personal blog of his which does not mention any figure let alone 35%. Such an approach to figures would be condemned by Research Fortnight, so it may be that Mr Bown is being used by the Government to lower expectations so that the final figures are not seen as too bad.

The figures that we do know (subject to assumptions such as an announced cut in welfare spending of £11bn) are that to tackle the structural deficit in this parliament, there would need to be average cuts of 14% in government departments over five years. The protection of the NHS against any cuts means other departments like the Department for Business, Innovation and Skills (BIS) need to make savings of 25%. This in itself will rile LibDems in government like Cable and Treasury chief secretary Danny Alexander, who were opposed to ring-fencing the NHS in this way because of the gearing effect on other government programmes.

Any relative protection given to defence and education (say, restricting cuts to 10%) would require cuts in departments such as BIS of 33%.

The coalition government is not responsible for the need to make cuts, and a Labour government – whatever the leadership candidates now say – would have had to deal with the deficit on a broadly similar scale, perhaps with a 70/30% split between spending cuts and tax rises compared with the 77/23% split of the coalition (itself different from the 80/20 pure Tory position). The cuts may also have been dragged out over a longer period.

Lord Drayson, Labour's former science minister, broke a long Twitter silence on science matters this morning to say that he was shocked by Vince Cable announcing major cuts to science budget on Radio Four. This is curious because the one thing that Cable did not do this morning on the radio or in his speech was announce major cuts. The mere acknowledgement that science spending will be hit in some way by the fiscal crisis should not shock anyone. Disappoint? Yes. Depress? Yes. Surprise? No.

The government is however responsible for deciding where those cuts fall the hardest and the success of the efforts of Cable and his deputy David Willetts should be judged on whether he is seen to seek to present the best arguments to the Treasury for maintaining science investment, and – given the scale of BIS cuts that follow – whether there is a relative protection for science within his department.

The next question is exactly how spending cuts will be implemented and what the government should, can and will do to influence that, which Cable dealt with in his speech today and which will benefit from close reading.