The Liberal Democrats would not follow the Tories’ ideological path of shrinking the state after the deficit is eliminated, according to Danny Alexander, the chief secretary to the Treasury.

The senior Lib Dem’s comments are part of an intensifying row between the coalition parties on future economic policy. Both agree that the deficit should be eliminated by 2017-18, but Alexander says that public spending should then rise in line with economic growth.

Both parties are trying to assert their distinctive agenda less than five months before the general election. Over the weekend, David Cameron accused the Lib Dems of being “all over the place” on the economy while Nick Clegg countered that the Tories were trying to kid the electorate on the scale of their plans to cut the deficit.

Speaking on BBC Radio 4’s Today programme on Monday, Alexander said: “What I think is important is that after 2017-18 we do not go in for an ideological path of shrinking the state and allow public expenditure to grow in line with the economy, and invest in things that matter as we have in fairness in this parliament.”

He said he would not set a target figure for the size of the state in relation to gross domestic product.

Alexander said it was legitimate for the two parties to set out their different views and different ideologies, adding they will continue to do so until May and insisting this does not undermine the government’s ability to keep Britain on the right economic path.

In an article in the Daily Telegraph, Alexander accused the Conservatives of pandering to Ukip in a pre-election panic.

He claimed the Tories would “inflict unnecessary pain” on the country because they were ideologically committed to shrinking the state and had a policy of “austerity for ever”.

Alexander wrote: “It is sad to see the Conservatives move away from the sensible, balanced approach of the coalition, to a more doctrinaire policy that would inflict unnecessary pain on the people of Britain.

“Who’d have thought that of the two parties that formed the coalition, it would be the Tories who would be blown off course?

“A mix of unfunded tax promises, harsh spending plans and pandering to Ukip may be born of pre-election panic, but it is not economically credible.”