Theresa May has denied the National Living Wage will be lower by the end of the decade than originally intended, appearing to contradict her own Budget book.

Speaking at Prime Minister’s Questions, Jeremy Corbyn – who branded the Government’s economic plan an “abject failure” – accused Ms May of abandoning George Osborne’s pledge for their “so-called national living wage paying at least £9 an hour by 2020”.

Asked “what is the new pledge on the living wage”, Ms May said: “The pledge on living wage is what is set out in the Autumn Statement and is at what it has always been.”

But the Office for Budget Responsibility (OBR) predicted last week that earnings are no longer expected to reach the level pledged by Philip Hammond’s predecessor at the Treasury. Last week it emerged the National Living Wage is now estimated to reach £8.80 in 2020.

According to Labour, the reduction in the National Living Wage could see 2.7 million people now directly face “a cut in their incomes of up to £1,324.96 by 2020”. On Sunday the Shadow chief secretary, Rebecca Long-Bailey, said Philip Hammond had “betrayed” working people.

Ms Long-Bailey added: “Philip Hammond has betrayed working people on low incomes, or those who he refers to as ‘JAMs’, as they will now be £1,300 worse off.

“There was a real opportunity to use last week’s Autumn Statement to stand up for working people, but yet again the Tories are carrying on with billions of pounds worth in giveaways to a rich few, while hitting many working families on the National Living Wage with cuts to their incomes.

“It further proves that only a Labour government can make an economic success of Brexit, to ensure no one and no community is left behind.”

The Government’s National Living Wage, introduced in April this year for those over 25, is currently set at £7.20 and will go up by 30p next year.