Theresa May's Government is skating on "incredibly thin ice" because it lacks legitimacy and a mandate for its policies, according to former Liberal Democrat leader Nick Clegg.
Mr Clegg said Mrs May's speech to the Conservative Party conference would "come back to haunt her" as he criticised her use of the phrase "citizens of nowhere" to describe global elites.
The former Lib Dem leader and deputy prime minister, who resigned after his party lost all but eight of its MPs in last year's general election, said it was "astonishing" that Mrs May's speech dismissed anyone who looked beyond Britain.
"I personally think this Government is skating on incredibly thin ice, because politically they got 23% of the eligible vote last year and Theresa May has no mandate of her own, foisting policies on the country for which she has no mandate, heading towards Brexit and an economic downturn without the faintest idea how to do that, with a very small majority," he said.
"That is not a recipe for triumphalism. Having said that, because of various things, the cards are all in the hands of the Conservatives now.
"They have almost unbridled support in the vested interests of the Press, they have an electoral system that flatters them and they are in an unassailable position because of what the SNP did to the Labour Party in Scotland.
"It doesn't matter who is leader - even if Tony Blair came back as leader reincarnated circa 1995, Labour cannot win again.
"The Conservatives have weak legitimacy, I think they are in terrible trouble over Brexit but they are politically unassailable."
Mr Clegg, who was speaking at the Cheltenham Literature Festival to promote his new book Politics: Between The Extremes, said Mrs May was right to see the Brexit vote as being much more than just about the EU.
"There is much I abhorred in Theresa May's speech and I think it will come back to haunt her," he said.
In reference to a quote from Mrs May's speech in which she said "if you believe you're a citizen of the world, you're a citizen of nowhere. You don't understand what the very word 'citizenship' means," Mr Clegg said: "To just condemn anyone who has this affinity of living in the wider world, that we can feel empathy, compassion and sympathy for other humans and continents, and to just dismiss all of those in that crucial passage in her speech as 'citizens of nowhere', I thought was an astonishing thing to say.
"What she did in that speech was re-invent history, as if the referendum on June 23 was a walloping majority for Brexit - but what it actually was, was a much closer, divided result.
"She was right though in that we shouldn't imagine what happened on June 23 is all about Europe. It was, as she rightly described, an anguished, enraged reaction against the status quo more generally.
"I don't think her recipe to deal with that is right but I think to frame what's happened in those terms and to address some of the things that erupted on June 23 are as much in our hands, as in Brussels', is right."
Mr Clegg said he was certain that there would be another coalition government because of the volatility in British politics but the junior partner must learn how not to pay the price.
But he said he did not see the scale of the Lib Dem defeat last year coming.
"I can honestly say, naive though it no doubt sounds now, I didn't expect the Liberal Democrats to plummet from 57 seats to eight," he said.
"I thought they were going to go down and it would be a tough election. Did I think it was going to be the absolute drubbing on the Liberal Democrats? No, I'm afraid I didn't. It was as brutal as it was unexpected."