Theresa May has insisted she is not concerned about the Tory opinion poll lead narrowing as she sought to recover from a U-turn over her flagship social care reforms.
Mrs May, who has seen a double-digit margin eroded in recent surveys but still enjoys a lead over Labour, said the only poll that counts is on June 8.
But in a major set-piece interview with the BBC's Andrew Neil she was challenged over the announcement that a cap on social care costs would now be included in her plans, having previously been ruled out.
"There's only one poll that counts in any election campaign," she said.
"That's the one that takes place on June 8 when people have actually cast their votes, when they have made that choice, which is a crucial choice.
"I think this genuinely is the most crucial election I have seen in my lifetime because it is about getting Brexit negotiations right, getting the right deal for Britain from Europe and going beyond that, a plan for a stronger vision for the future."
She added: "I have never taken anything for granted in this election."
Mrs May, who repeated her "strong and stable" leadership slogan despite the reversal on social care policy, denied her manifesto was "uncosted and half-baked".
She said: "No, what we have set out in our manifesto is a series of policies which address what I see and I think are the five great challenges that we face as a country."
Mrs May sought to highlight the looming Brexit negotiations as a reason to vote Tory rather than Labour.
"There's only going to be a choice between two people as to who's sitting opposite those 27 European countries, me or Jeremy Corbyn," she said.
Challenged about the social care U-turn, Mrs May said: "What I've done today is I've seen the scaremongering, frankly, that we've seen over the weekend. I've seen the way that Jeremy Corbyn wants to sneak into Number 10 by playing on the fears of older and vulnerable people, and I've clarified what we will be putting in the green paper which I set out in the manifesto."
Pressed on how the Conservatives would pay for the promise of an additional £8 billion for the NHS, Mrs May said: "In our manifesto we've put some examples of how we're going to change the way money is used.
"On winter fuel payments, for example, we will means-test that. That money will go into health and social care."
Asked where the money would come from, she said: "What we have done, if you look at our record, is shown that we can put record sums of money into the National Health Service at the same time as we're ensuring that we're building that strong economy. And that's what we'll do for the future.
"Our economic credibility is not in doubt. It's the Labour Party who's in the dock when it comes to responsibility."
Asked again where the money would come from, the Prime Minister said: "What we will do in the future is ensure that we have the strong economy, growing economy, that enables us to generate the funds to put into our public services."