Theresa May mocked Jeremy Corbyn for an economic slip during Prime Minister's Questions, claiming it showed why it is best he is in opposition.
The Prime Minister defended the Government's economic plan and cited positive claims from the International Monetary Fund (IMF) following criticism from the Labour leader
But Mr Corbyn accused the PM of selectively quoting the IFS - the Institute for Fiscal Studies - as he said those people who are "just getting by are suffering all the pain for no gain".
Mrs May replied: "I think, given that you can't differentiate between the IMF and the IFS, it's probably a good job you're sitting there and I'm standing here."
Mr Corbyn later renewed his attack on the Government over social care funding and questioned why not a "single penny more" had been offered in last week's Autumn Statement.
Speaking during PMQs, Mr Corbyn said the Autumn Statement "revealed the abject failure" of the Government's economic strategy.
He asked Mrs May to accept that her predecessor David Cameron's "long-term economic plan was actually a failure".
The PM replied: "I'll give you some facts - the IMF says this will be the fastest growing advanced economy in the world this year, unemployment is down, we have record numbers of people in employment and we have companies like Nissan, Jaguar Land Rover, Honda, Arm, Google, Facebook, Apple investing in the UK - securing jobs here in the United Kingdom.
"That's what a good economic plan does."
Mr Corbyn said the Conservatives had claimed the economic deficit would be eradicated by 2015, then 2020 and "now it's been advanced to whenever in the future".
He went on to Mrs May: "Since you quote the Institute for Fiscal Studies, I think you've been a little bit selective, because they also went on to say that the prospects for workers over the next six years was 'dreadful', it went on to say 'creating the worst decade for living standards since the last war and probably since the 1920s'.
"Isn't it fair to say that those just getting by are suffering all the pain for no gain?"
Mrs May replied: "I have to say to you, I think given that you can't differentiate between the IMF and the IFS, it's probably a good job you're sitting there and I'm standing here."
The PM then listed measures - including increasing the minimum wage and the personal tax allowance - which she said are helping people who are struggling to get by.
Mr Corbyn said wages have "stagnated", home ownership is falling, homelessness "has doubled" with queues at food banks "rising every day".
He then raised concerns about welfare cuts, which led Mrs May to claim the Labour leader "believes in a welfare system where people are able to live on benefits".
Mr Corbyn also said the Government has "abandoned" former chancellor George Osborne's pledge for the so-called National Living Wage to pay at least £9 an hour by 2020.
He asked: "What is the new pledge on the living wage?"
Mrs May was heckled by the Opposition as she replied: "The pledge on the living wage is what is set out in the Autumn Statement, as it always has been."
Moving on to social care, Mr Corbyn said: "1.2 million people are lacking the care they need. Why was there not one single penny more for social care in the Autumn Statement?"
Mrs May replied: "There's absolutely no doubt that the social care system is under pressure. We recognise that.
"If you just look at the fact that there are one million more people aged over 65 today than there were in 2010, we see the sort of pressures on the social care system.
"But that's why the Government has already acted to put more money into the social care system ... £3.5 billion extra through the Better Care Fund and more money through the social care precept.
"But it's also important that local authorities and the NHS work together to ensure, for example, that people have the social care they need so they're not ending up blocking beds in hospital.
"There's some very good practice up and down the country and sadly there's some not so good practice.
"What we need to do is make sure everybody is giving the best possible service to people who need it."
Mr Corbyn said there is a "tragic parallel going on between an underfunded NHS and underfunded social care system" across the country.
He suggested Mrs May should listen to Izzi Seccombe, Conservative leader of Warwickshire County Council, who said her authority has been "cut to the bone" with concerns over funding.
Mrs May said £3.8 billion extra cash is being given to the NHS this year, adding: "Under Labour's plans we would have seen £1.3 billion less going into the National Health Service.
"Social care funding is going up under this Government. At the last election, the shadow chancellor (Ed Balls), lately of Strictly fame, said local authorities would get not a penny more."