The Prime Minister was responding to a member of the audience at an election special of BBC Question Time, who asked: “My wage slips from 2009 reflect exactly what I'm earning today. How can that be fair, in the light of the job that we do?“
Another nurse said the 1 per cent cap on annual public sector pay rises had meant a real-terms decrease in his salary of 14 per cent since 2010, adding: “So don't tell us we're getting a pay rise.”
The Prime Minister said she recognised the job done by NHS staff but that “hard choices” had to be made across the public sector.
"We did that because of the decisions we had to take to bring public spending under control, because it wasn't under control under the last Labour government," she added.
"And I'm being honest with you in terms of saying that we will put more money into the NHS, but there isn't a magic money tree that we can shake that suddenly provides for everything that people want."
Ms May repeated the phrase, which was also used by Amber Rudd when she represented the Tories in a previous BBC debate, when challenged on the issue.
The moderator, David Dimbleby, asked whether the Prime Minister could “sleep happily”, adding: ”Do you think it is fair that the nurses get just a 1% increase year in, year out, regardless of inflation, so they get poorer, so some of them we're told go to food banks?”
An audience member accused Ms May of “cutting NHS spending while cutting tax for the rich”.
“We have to make sure that we are managing our money carefully because at the end of the day there isn't a magic money tree that suddenly delivers all the money everybody wants for the spending everybody wants,” she responded.
Her comments provoked strong criticism on social media, where critics pointed out that there wasn't’t a “magic nurse tree, a magic doctor tree, a magic policeman tree or a magic teacher tree” either.
Others called the Prime Minister “callous and incompetent”, saying her response was a “disgrace”.
Jeremy Corbyn, who was grilled separately after the Prime Minister refused to attend head-to-head debates, came under fire over Trident, anti-Semitism and whether he regards the IRA as a terrorist group.
An audience member said it was “disconcerting” that the Labour leader refused to say whether he would launch a retaliatory nuclear strike in the event of an attack.
"I would view the idea of having to use a nuclear weapon as something that was resulting in a failure in the whole world's diplomatic system,” Mr Corbyn said.
"There has to be no first use, there has to be a process of engagement to bring about, ultimately, global nuclear disarmament. It's not going to happen quickly, it's not going to happen easily, but we have to have that wish."
He was also forced to defend the Labour Party's failure to expel Ken Livingstone for allegedly anti-Semitic remarks and quizzed on whether its manifesto is "just a letter to Santa Claus".
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