JEREMY Corbyn has pledged to give nearly six million British workers a pay rise within months of Labour winning power in 2020 by raising the national minimum wage to at least £10 an hour.

The flagship policy, announced last year, would leave full-time employees on basic earnings better off by more than £2,500 while 21 to 24-year-olds on lower wage rates would be in line for a £4,500 hike.

However, the declaration by the Labour leader has been branded “reckless” by free market think-tanks, which argue that putting up the rate by such an extent – it is due to rise to £8.75 an hour for most workers by 2020 – would simply endanger the jobs of low-paid workers as companies would struggle to fund the higher wage bills.

During a campaigning visit to Luton ahead of May’s local elections, Mr Corbyn said: “Low pay blights the lives of huge and growing numbers in our country and fuels widening inequality. The Government's re-branding of the minimum wage to the national living wage hasn't dealt with the real problems of low pay and rising cost of living.

"That's why Labour will raise the legal minimum wage for all to at least £10 an hour by 2020, giving more than five and a half million people a pay rise in the process.”

The party leader said that Labour's real living wage would immediately boost the incomes and opportunities of more than one fifth of Britain’s workforce, especially in sectors such as retail, care and hospitality.

"We know that where work pays, living standards rise and reliance on benefits falls. This is the right thing to do and a Labour government will be committed to re-balancing our economy so that no one and no community is left behind," insisted Mr Corbyn.

Under Labour’s policy, some 5.6m workers would see their pay go up. The party has said that workers in Northern Ireland, the East Midlands and Yorkshire would be among those to benefit most with one in four affected.

"Theresa May promised to be a champion of working people; she has failed,” declared John McDonnell, the Shadow Chancellor.

"The Tories are taking the country backwards; Labour will stand up for working families making them £2,500 a year better off in 2020. Only Labour will take the action needed to end the Tories' economic failure and introduce a real living wage of £10 an hour by 2020," he added.

But Sam Bowman, Executive Director of the Adam Smith Institute, said: "Labour’s commitment to raise the minimum wage to £10 an hour is reckless and ignores the potential costs of such a move.

“We know that increases to the minimum wage have to come from one of three places: either through lower wages or employment for other workers; lowered company profits or higher prices. The evidence is pretty strong that higher minimum wages kill jobs, whether through direct layoffs or by slowing down new job creation and this effect seems to get stronger the higher the minimum wage level is.”

Mark Littlewood, Director General at the Institute of Economic Affairs said: "Raising the minimum wage so sharply would put the jobs of low-skilled workers and those in part-time work at risk. We have already seen companies in the retail, food and social care sectors scrap in-work perks, withdraw overtime and Sunday pay, and cut hours in an attempt to offset the costs of the National Living Wage - proof that arbitrarily instituting wage increases does nothing for the workers it is attempting to help.

"The ones who will really feel the effects of such a measure are those in part time work, a large proportion of whom are women, young workers and ethnic minorities; a disproportionate number of whom work in low-paid or low-skilled jobs.

“It's quite baffling how the Labour Party are even contemplating a policy that will hurt the groups of people they claim to protect.”

Mr Littlewood added: "And why stop at £10? Why not £20? Or £100? Rather than considering the general health of the economy and firms' ability to pay, Mr Corbyn seems to have irresponsibly plucked a number out of the sky that feels right rather than one that makes economic sense."

Meantime, Tory backbencher Chris Philp, who sits on the Commons Treasury Committee, said: “The only way you can raise the minimum wage is with a strong economy. That’s how this government has increased it from £6.70 in 2015 to £7.50 today and will increase it to £8.75 by 2020.

“Jeremy Corbyn would crash the economy with £500 billion of extra borrowing, hurting investment into this country and damaging jobs.”