Keir Starmer has demanded an early general election to end the chaos caused by Boris Johnson and told the Tories to "put their money where their mouth is".
Speaking after being cleared by police over "Beergate", the Labour leader said the country was "stuck in a dangerous rut" and needed a "fresh start" with a change of Government.
He threatened to force a vote of no confidence next week if Mr Johnson continues to cling onto power.
Mr Starmer insisted Labour had a plan for the country, adding: "If there's a general election, this Government will fall."
The Labour leader categorically ruled out a pact with the SNP but was less forceful in his denial of a deal with the Liberal Democrats, as he spoke to reporters at Labour HQ.
It comes after Mr Starmer and his deputy Angela Rayner were cleared by Durham Police over allegations they broke Covid rules during campaigning for the Hartlepool by-election last year.
Dubbed Beergate by right-wing newspapers, the row centred on grainy footage of Mr Starmer drinking a beer and having a takeaway with activists on the campaign trail.
The force said today that it would take no further action over the incident, in a major boost to the Labour leader who had vowed to resign if he was fined.
Mr Starmer told reporters: "People said to me I was taking a risk by saying I would step down if I was fined. But it was never about that.
"For me it was a matter of principle. It shouldn't be controversial to say those who make the law can't break the law. But we have to set the bar far higher than that."
He said it was a "very good week" for Labour after Boris Johnson said he would quit on Thursday and the cloud of the Durham Police probe was lifted.
Mr Starmer went on: "My challenge to the Tories is not 'who's your next leader gonna be', but 'give us the change we really need, let's have a general election, let's have a change of government, a fresh start for our country'."
Asked if it was the right time for a general election, he said: "Yes, we've been stuck in the middle of a cost-of-living crisis with a Government that can't deliver, with a Prime Minister who is not fit to be Prime Minister...
"It's not just about the last few months either. We've had 12 years of stagnation, 12 years of low growth. So Britain deserves that fresh start that can only come with a change of government."
He added: "If there's a general election, this Government will fall and we've got a plan for the country."
Mr Starmer confirmed he would push for a no confidence vote next week if Tories fail to remove the PM, who should leave No 10 "straight away".
"The duty is on the Conservative Party to do the right thing, and obviously there are meetings early next week with the '22 committee. So it's for them to do the right thing," he said.
"If they don't we will step up with a vote of no confidence."
He was grilled by reporters on whether Labour would agree a pact with the SNP or the Liberal Democrats - a key Tory attack line ahead of the next poll.
But Mr Starmer insisted: "There is no basis for an alliance under a Keir Starmer government, between Labour and the SNP. Full stop.”
He was less forceful on Sir Ed Davey's party, saying: "So far as the Lib Dems are concerned, we want a Labour majority.
"We want to deliver on our mission and that is what we are going to do.
"We are fighting for a majority Labour government to deliver our mission."
