Britain is through the worst of the economic storm, Sir John Major said today.
The Conservative former Prime Minister said data showed the UK's recovery has begun, with employment and the stock market rising.
He also urged Tory MPs to rally behind David Cameron amid mutterings about his leadership, and predicted a two-tier Europe within a decade.
Speaking on the 20th anniversary of Black Wednesday, which marked Britain's dramatic exit from the exchange rate mechanism, Sir John said the UK's economic recovery was under way, despite gloom surrounding the eurozone crisis.
He likened today's UK economy to the early 1990s when Chancellor Norman Lamont was widely mocked for claiming he could see the "green shoots of economic spring".
The ex-Prime Minister said: "Norman Lamont was taken to pieces by commentators for suggesting there were green shoots, but in retrospect we can see that Norman was right.
"Recovery begins from the darkest moment. I'm not certain, but I think we have passed the darkest moment."
Sir John told BBC1's Andrew Marr Show there were "oddities" in economic data.
He added: "Why in the depths of this recession is employment growing? Why is industrial production going up? Why has the stock market risen?
"There are things happening out there that will become apparent and we don't quite know why or how.
"My guess - and this is something a minister can't say but I can - is that in due course we will find that passed the bottom."
Sir John, whose seven-year premiership was blighted by Conservative splits on Europe, said the eurozone crisis was pushing the 17 countries in the currency union closer together.
He said the process could take up to 10 years and would spark a UK referendum on Britain's relationship with the European Union.
"What you're now seeing, out of failure and not success, is the euro core looking to integrate further, much more towards a federal structure," he said.
"That offers an opportunity for us to clean up one of the long-running sores of British politics, which is our relationship with the rest of Europe."
Sir John backed Mr Cameron to lead the Conservatives into 2015 General Election, dismissing claims London Mayor Boris Johnson could oust the Tory leader.
Sir John, who faced challenges to his leadership and continual whisperings from his enemies within the party, said there was "nothing surprising about people being critical when times are tough".
"It is an inevitability of politics, but I would have thought if the Conservative Party has learned anything in the last 20 years, it is that regicide is not a good idea," he said.
Sir John described Mr Johnson as "a very attractive and able and intelligent politician", but added: "Boris isn't in Parliament, Boris hasn't said he wishes to become Prime Minister - quite the reverse.
"David Cameron is Prime Minister, he's going to remain Prime Minister and he's going to contest the next election and I very much hope he's going to win it."
Shadow foreign secretary Douglas Alexander told Sky News' Murnaghan show voters had lost patience with the Government's economic policies and blamed ministers for the double-dip recession.
He said: "We are seeing the deficit going up, we are seeing unemployment far too high, we are seeing three quarters of negative growth."
Transport Secretary Patrick McLoughlin said the Government would not be diverted by "mutterings".
"I've seen mutterings about lots of prime ministers' leaderships in my time," the former chief whip told the Murnaghan programme on Sky News.
"There was quite a lot of mutterings about Margaret Thatcher's leadership - everyone seems to forget that now. There was mutterings about John Major's leadership and there was a huge row about Tony Blair's leadership.
"In fact Tony Blair for the last five years of his premiership had a chancellor trying to undermine him. At least we've got a chancellor who is working full steam with the prime minister to deal with the economic problems we inherited."
He added: "My message is the Government's getting on with the job and we won't be diverted by side issues."
Former defence secretary Liam Fox also dismissed rumours surrounding Mr Cameron's leadership, telling Murnaghan: "It's nonsense that there's a threat to the Prime Minister."
The Tory MP added: "We have a very good Prime Minister, we have got a very good leadership in the Conservative Party. We need to fall behind it.
"We need to have a very robust debate, but having a robust debate isn't the same as undermining the leadership."
Right-winger Dr Fox, who quit the Cabinet last October over his relationship with his adviser Adam Werritty, called for a tougher approach to Europe, which would please backbench Conservatives.
"It is very clear how that there is a very wide consensus in this country that there has to be a change in the relationship," said Dr Fox, who favoured a deal focused on trade.
"Right across the political spectrum, certainly across the Conservative Party, there is an appetite for a renewed relationship."