Theresa May has claimed that raising the minimum wage for those under 21 and under 18 to match the rate paid to everyone else “will cost young people jobs”.
Quizzed by Jeremy Corbyn about the difference, the Prime Minister claimed that it would lead young people being less well off.
Labour has pledged to abolish the youth rates of the NMW if they win the next election.
Mr Corbyn said: "If you are old enough to do the job, then you are old enough to be paid the wage to do it."
But Theresa May said that "the impact of the policy he announced will be to cost young people jobs".
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The Prime Minister then quoted the IFS saying that the impact on young people would be "negative".
She added: "We don't need to rely on quotes to know what would happen to young people, we just look at the record of the last Labour government.
"Under that government youth unemployment rose 44%, under the Conservatives it has fallen by 50%."
But Mr Corbyn said the government was intent on "punishing young people".
"They have trebled tuition fees, abolished the Educational Maintenance Allowance and cut Child Benefit," he added.
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Currently the NMW is £8.21 an hour, unless you are under 18, whem it drops to £6.15.
That is £2.06 less an hour for what could be the exact same job.
For people under 21 it is £7.70 or 51p less an hour for the same work.
If you are a under 22 and an apprentice you can be paid as little as £3.90 an hour.
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The claim that changes to the minimum wage would cost jobs were part of the Conservatives original objections when it was introduced in 1999 - but it turned out to be dead wrong .
It came as the Government was accused of being "in the pockets of an elite few" by Jeremy Corbyn as questioned the PM about the Mirror revealing that the Tories trousering are cash from almost half the UK's richest hedge fund tycoons .
Theresa May hit back at Prime Minister's Questions, saying that "income inequality is down since 2010" when the Tories came into office, adding her party "want everyone to be better off, everyone to have good jobs and everyone to have a better life".
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But the Labour leader said the Nobel Prize-winning economist Sir Angus Deaton had said the UK "risks having extreme inequality levels of pay, wealth and health", asking: "Is that something the Prime Minister is proud of?"
Mrs May replied that the "top 1% are contributing more income tax than at any point under the last Labour government".
