Boris Johnson and Jeremy Corbyn have clashed over the NHS, Brexit and leadership at the last Prime Minister's Questions before the general election.
The Labour leader said voters had a "once in a generation" chance to save the NHS, which was in "greater danger" than at any time in its history.
But the PM warned of "economic catastrophe" if Labour got into power.
Meanwhile, some senior MPs, including Culture Secretary Nicky Morgan, have said they will not be standing.
Announcing that she would not contest her Loughborough seat again, Mrs Morgan cited the "clear impact" that being an MP and the "sacrifices involved" had had on her family.
"The abuse for doing the job of a modern MP can only be justified if, ultimately, Parliament does what it is supposed to do - represent those who serve in all areas of public life, respect votes cast by the electorate and make decisions in the overall national interest," she wrote.
For the first time in 18 years I won't be a candidate in the next General Election. I've loved being #Loughborough's voice in Westminster since 2010 & being DCMS Secretary - & I look forward to supporting the PM, Government, Conservative Party and my successor in the future pic.twitter.com/xhH11bxd3C— Nicky Morgan MP (@NickyMorgan01) October 30, 2019
In recent days, a number of prominent female MPs elected since 2010 - including Amber Rudd, Heidi Allen and Mims Davies - have drawn a line under their frontline political careers - joining others such as Justine Greening and Claire Perry.
Lib Dem MP Sarah Wollaston said women were being "hounded" out of politics.
So many women from across the political spectrum are now being hounded out of politics. I used to hold regular open public meetings but, like many MPs, I’m advised not to advertise where I will be in advance. That has in effect shut them down.— Sarah Wollaston MP (@sarahwollaston) October 30, 2019
Sir Alan Duncan, one of a number of former ministers quitting, said the "coarse" nature of political debate on what he dubbed "anti-social media" was having an impact.
Meanwhile, peers have approved the legislation needed to bring about the 12 December election.
The House of Lords passed the early election bill - which was approved by MPs on Tuesday - in less than four hours, with no changes.
Final Commons clash, for now
In their final encounter in Parliament before the election, the two leaders exchanged barbs over their political values and disputed their parties' respective records on the NHS.
The Labour leader accused the PM - who he has challenged to a one-on-one TV debate - of running down the health service, saying cuts to funding had contributed to rising waiting times for cancer treatment and operations.
He said a Labour government would reverse what he said was the growing privatisation of the NHS, saying it existed to "make people better, not make the wealthy few richer".
"The choice at this election cannot be clearer," he said.
"People have the choice to vote for real change after years of Conservative and Lib Dem cuts, privatisation and tax handouts for the richest."
Mr Johnson said he agreed voters faced a "stark choice" between a government spending "unrivalled" sums on the NHS and a Labour party that would "wreck the economy".
Dismissing the Labour leader as an "Islingtonian protester" rather than a real leader, he said Mr Corbyn's "flip-flopping" over Brexit would lead to more years of "toxic, tedious, torpor".
While 2020 would be a "wonderful year" under a Tory government, he said electing Jeremy Corbyn would result in further referendums on Europe and Scottish independence.
"That is the future. Drift and dither under the Labour Party or taking the country forward to a brighter future under the Conservatives. That is the choice the country faces."
The election comes after the EU extended the UK's exit deadline to 31 January 2020 - although Brexit can happen earlier if a deal is agreed by MPs.
What happens next?
- The Early Parliamentary General Election Bill is likely to receive Royal Assent - when the Queen formally agrees to the bill becoming law - in the next 48 hours
- On Monday 4 November, MPs are due to elect a new Speaker to replace John Bercow
- Just after midnight on Wednesday 6 November, Parliament will be shut down or "dissolved" - meaning every seat in the House of Commons becomes vacant
- The electoral authorities have set a deadline of the end of Tuesday 26 November for people to register to vote.
- The cut-off point to apply for postal votes is the same day, but at 17:00 GMT.
Speaking outside Parliament, Lib Dem leader Jo Swinson said her party was "on the up" and had a larger war chest at its disposal than ever before going into an election.
"Make no mistake, I stand ready to take on Boris Johnson and Jeremy Corbyn as a candidate to be prime minister," she said.
"We have a bold vision to stop Brexit and build a better, brighter future for the country."
For the Scottish National Party, Scotland's First Minister Nicola Sturgeon said an election was an opportunity for the country to hold another independence referendum.
"A win for the SNP will be an unequivocal and irresistible demand for Scotland's right to choose our own future," she said.
But the Scottish Conservatives claimed voting for their party would keep Scotland in the UK.
Meanwhile, an attempt by Boris Johnson to unite his party by re-admitting 10 Tory Brexit rebels has been hit by a row over the party's refusal to give the whip back to Amber Rudd - the former home secretary who has said she is standing down as an MP.
Electoral pacts and coalitions
The smaller parties are already talking about striking deals with each other, which could see candidates standing aside in areas where their Remain-supporting rivals have a better chance of winning.
Ms Swinson said there were a "small number of seats" where "arrangements" could be struck with other parties to give an anti-Brexit candidate the best chance of winning.
Green Party co-leader Jonathan Bartley told BBC Breakfast it was "no secret" that the Greens were "talking to the Lib Dems and Plaid" but "nothing has been finalised".
He said the ideas was to get "a big block of MPs in Parliament who want a people's vote, want to remain in the EU because they think it's best for the UK to do that".
Plaid leader Adam Price said his party was "open to working with others to secure our European future".
Details of which candidates are standing and where will be published at 17:00 GMT on 14 November - as will information about the location of polling stations.
The party leaders are also facing questions about whether they would form a coalition, if the election resulted in another hung Parliament.
Asked if she would join forces with Labour or the Conservatives, Jo Swinson said: "I can't be clearer - neither Boris Johnson nor Jeremy Corbyn is fit to be prime minister."
Labour's John McDonnell told BBC Breakfast: "There will be no deals, no coalition. We will go in as a majority government. If we don't win an overall majority, we will have a minority government."