A supertax on high earners should be considered as part of Gordon Brown’s autumn fight-back, a minister says today.

Ivan Lewis, writing in The Sunday Times, calls on the government to introduce a new economic package to bail out the hard-pressed middle classes – possibly paid for by new taxes on the rich.

The health minister warns that urgent steps must be taken to protect the living standards of the “mainstream majority” of comfortably off voters who swept Labour to power in 1997.

His intervention ends the brief summer truce in Labour’s civil war following the government’s disastrous defeat in the Glasgow East by-election and is likely to be the first of a series of provocative moves by MPs disillusioned by the party’s flagging fortunes.

A YouGov poll for The Sunday Times today shows David Cameron’s Tories have a 20-point lead over Labour, which is stuck on 25% support.

Several ministers are known privately to share Lewis’s view and are expected to speak out in coming weeks – piling pressure on Alistair Darling, the chancellor, to do more to help struggling middle-earners.

Lewis points to families who take two holidays a year, belong to private gyms and eat in restaurants, but struggle to pay soaring bills, as the group in need of help.

“If, as a result of the current economic situation, the only way to help hard-pressed middle-class families is to ask the highest earners to pay more, then serious consideration should be given to that,” he writes.

Last month a former minister, Chris Leslie, called for an extra 10p in the pound tax for earnings above £250,000, the threshold Lewis is believed to favour. The Treasury estimates this would yield £3.5 billion a year, about the same amount as it collects from inheritance tax.

Lewis warns in his article that the electorate is “angry and disappointed” and says Labour has a “duty” to make tax and spending decisions which demonstrate the party understands the pressure of rising food, fuel and utility bills.