In an urgent general election appeal, the Prime Minister emphatically questioned the Labour leader's patriotism and his will to get the best deal for the UK out of talks with Brussels.
She also insisted the veteran hard-Left socialist was simply incapable of battling for Britain over the negotiating table.
"He doesn’t believe in Britain, he doesn’t have a plan, he doesn’t have what it takes," she said.
Her appeal marked a further hardening in tone for the Tory election campaign following concern that her party's opinion poll lead over Labour has narrowed with voting day less than a week away.
Tory jitters were eased last night when a new poll of polls suggested Mrs May is still on course to gain a significant Commons majority in the general election on June 8.
Five out of six polls collated by news service Bloomberg forecast a majority of at least 40 seats after the contest, with one pollster claiming the figure go up to 200 seats.
Theresa May has issued a stark warning that Labour could turn Brexit into a disaster
He doesn’t believe in Britain, he doesn’t have a plan, he doesn’t have what it takes
Mrs May used a speech deep in former Labour territory in the North East of England to set out her vision of a prosperous future for the country outside the EU.
"A stronger, more secure and prosperous nation; a brighter, fairer future for all – that is what excites me about the years ahead," she told Tory supporters in Middlesbrough.
In a swipe at Mr Corbyn, the Prime Minister said the election was "so important" because "make no mistake, not everyone shares this view".
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Savaging Labour's leadership team, she said: "They say we’re too small and too insignificant, that Britain can’t do it, that the British people are not up to the task.
"In short, they don’t believe in Britain. And if that’s where you start, you have no hope of getting the right deal for Britain in Europe.
"You can’t negotiate the right Brexit deal for Britain if you don’t believe in Britain."
She added: "What we know in this election is that the only other person that can be Prime Minister in seven days’ time is simply not up to the job.
"He doesn’t believe in Britain, he doesn’t have a plan, he doesn’t have what it takes."
Mrs May said Mr Corbyn's attention "wouldn’t be on trying to negotiate a deal for Britain in Europe, but on trying to stitch up a deal with Nicola Sturgeon and the rest".
The Prime Minister said that Jeremy Corbyn ‘does not believe in Britain’
"Yet it is on the success of those critical Brexit negotiations that everything else we want as a country will depend," she said.
"If we don’t get Brexit right – if we don’t make a success of the next five years – our economic prosperity will suffer, jobs and livelihoods will be put at risk, and with them the security and peace of mind of working families."
Mrs May also insisted that voters knew exactly what choice they were making when they backed leaving the EU in last year's referendum.
"They did so with their eyes open; they knew that it would not be straightforward," the Prime Minister said.
"They knew the road ahead may be uncertain but they believed that it would lead towards a brighter future for their children – and their grandchildren too.
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She questioned the Labour leader’s patriotism and his will to get the best Brexit deal
"So with determination and characteristically British quiet resolve, they defied the establishment, ignored the threats and made their voice heard.
"I respect that decision and am clear about what needs to be done. It is time to act on their instruction, to deliver their will.
"It is time to respect the decision of the British people and take Britain out of the European Union."
Pledging to give her utmost to win a good Brexit deal for the country, Mrs May said: “I make this commitment to you and this commitment to Britain – if we stand together, and you vote to back me and strengthen my hand, I’ll fight to get the best Brexit deal for Britain.
“I’ll stand up for Britain, and fight for Britain, to guarantee our economic security, to deliver better-paying jobs, a good school place for every child,real technical education – and extra funding, every year, for our schools and a strong NHS.
Mrs May also insisted Mr Corbyn was incapable of battling for Britain in Brexit talks
“And I’ll stand up for Britain to ensure we control and reduce immigration when we leave the EU.”
Bloomberg's survey of polls collated data from leading poll firms including ICM, YouGov, Ipsos MORI, ComRes, Opinium and Survation.
Martin Boon, of ICM, said: “Things can change at short notice but my expectation is that the Tories will cruise home with a working majority probably in the region of 80 to 100 seats.
"I don’t think there’s a possibility of Labour having any kind of majority.”
Andrew Hawkins, chairman and founder of ComRes, said: "We are still expecting the majority to be north of 70 and quite possibly north of 100.
"The sheen has come off Theresa May’s honeymoon but it hasn’t actually shifted voting behaviour yet."