The rescue plan for social care has been plunged into further confusion, after a government minister said it would be wrong to hike national insurance to fund it.

       Boris Johnson and Rishi Sunak are close to an agreement that is expected to hike the tax by 1 per cent – but the Conservative manifesto promised not to increase any of the major taxes.

       Kwasi Kwarteng, the business secretary, appeared to blow a hole in the idea, saying: “That is what it says on the manifesto. I don’t see how we could increase national insurance.”

       Extraordinarily, the increase would have been announced this week, but for the chaos at the heart of the government that forced both the prime minister and his chancellor into isolation.

       It had already been widely attacked as unfair, because it would load extra taxes on younger and lower-paid workers – while pensioners would escape, because they do not pay national insurance.

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       The Resolution Foundation think-tank condemned “a terrible way to raise the funds required” and both senior Tory and Labour politicians echoed the criticism.

       Speaking to Sky News, Mr Kwarteng opened up some wriggle room over tax rises, by saying “things have been very flexible over the last 18 months, we’ve lived through an unprecedented time”.

       The long-delayed social care plan would come “by the autumn”, he said, adding: “I don’t think we’ll put up national insurance in that specific....”, before tailing off.

       The business secretary also cast doubt on the pledge to lift isolation rules for double-vaccinated people who are close contacts of a Covid case on 16 August, warning it may not go ahead.

       The timetable had already been attacked as an unnecessary delay, coming 5 weeks after all other Covid rules were lifted and blamed for the “pingdemic” of mass isolation of workers.

       But, asked if it would “definitely go ahead”, Mr Kwarteng said: “We always review the information a week before and then we make the decision,” – adding he was keeping his “fingers crossed”.

       Increasing national insurance by 1 percentage point – for both employers and employees – would raise ￡10bn a year and would probably be dubbed a new “health and social care levy”.

       Initially, it would be used to cut alarming NHS waiting lists for treatment, which are feared could rise from 5.3 million to 13 million.

       It would then be spent to cap care costs, along the lines of a decade-old proposal to limit costs to ￡50,000 so families do not end up selling their homes, and plug growing gaps in care treatment.

       Without a specific tax rise for social care – and with further huge spending cuts to come, in the autumn – Mr Sunak would have to increase borrowing further to tackle the crisis, which he is opposed to doing.