He said claims of ending austerity would be a “great big Conservative con” if there is no increase in public sector spending announced in the budget on 29 October.
Mr Corbyn seized on the pledge – contained in Mrs May’s keynote speech at the Conservative Party conference last week – asking the PM how she intends to end the cutbacks for police, the NHS, schools, councils and disabled people.
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Mrs May stuck by her conference pledge and told MPs that while austerity would be coming to an end, “what is not being brought to an end is fiscal responsibility”.
She claimed Labour would wreck the economy if it got back into power, with their vision for the country costing £1tn.
The issue was front and centre of the first PMQs since party conference season and comes ahead of Chancellor Philip Hammond’s budget on 29 October.
Mr Corbyn chose to lead on it when he rose to ask questions, and started by raising cuts to mental health budgets.
He said: “Today there are 5,000 fewer mental health nurses than there were in 2010.
“The prime minister said last week that austerity is over.
“When will austerity be over for the mental health services?”
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Mrs May said her government was putting “record levels of funding” into mental health, adding: “If he’s saying to me that we still need to do more in mental health, I say yes, we do.
“That’s exactly why we’re setting out further steps today to improve the mental health of children and young people.”
When pressed further by the Labour leader, the PM said she had been “very clear” that there were “better times ahead for people, we will see debt falling and we will see support for our public services going up”.
She added: “Austerity is being brought to an end.
“What is not being brought to an end is fiscal responsibility.”
Mr Corbyn claimed “eight years of painful austerity” had left the country in a sorry state, telling MPs: “Poverty is up. Homelessness and deaths on our streets is up. Living standards down. Public services slashed. A million elderly are not getting the care they need. Wages have been eroded.
“And all the while, billions were found for tax giveaways for big corporations and the super-rich.
“The prime minister declared she is ending austerity.
“But unless the budget halts the cuts, increases funding to public services, gives our public servants a decent pay rise, then isn’t the claim that austerity is over simply a great big Conservative con?”
The PM said the Tories had a record in government to be proud of, telling the Commons that wages are on the rise, the minimum wage has been increased and added there were one million fewer people in “absolute poverty”.
She also defended the controversial Universal Credit welfare reforms, saying the policy will see one million disabled households get £110 a month more.
Mrs May said income tax cuts, a freeze in fuel duty for the ninth year in a row and the energy price cap were all helping working people.
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She added: “We know what would really hurt working people – Labour’s plans would cost £1tn of people’s money.
“Uncontrolled borrowing, spiralling taxes, working people paying the price of Labour – yet again, Labour taking us back to square one.”