With just two days to go to the June 8 General Election, Conservatives have stepped up their assault on Jeremy Corbyn, denouncing him as "muddled-headed" on terrorism and weak on Brexit.
Theresa May and Boris Johnson unleashed attacks on the Labour leader as a brace of opinion surveys suggested the UK may be heading for a hung Parliament on Friday.
And Conservatives highlighted a Labour manifesto promise to scrap marriage tax allowances, which they said could cost 4 million couples up to £230 a year.
Meanwhile, Labour sought to maintain their campaign momentum with six simultaneous celebrity-packed rallies around the country addressed by Mr Corbyn by satellite link on Tuesday evening.
Speaking from Birmingham to thousands of supporters in Barry, Brighton, Glasgow, London and Warrington, the Labour leader was set to say: "While the Conservatives promise five more years of a country run for the super-rich and cuts for everyone else, Labour will transform Britain by investing in infrastructure and new industries and rebuilding the NHS and our public services.
"On Thursday, the British people will go to the polls and have the chance to vote for a government that will transform our country for the many, not the few."
In a high-profile speech in County Durham, Mr Johnson warned that Brexit talks due to start later this month would "founder" if Mr Corbyn wins power.
Labour's "herbivores" would be "eaten for breakfast" by Brussels bureaucrats, and Mr Corbyn's position would be fatally undermined by the "jabbering" of possible coalition partners Nicola Sturgeon and Tim Farron demanding Britain stays in the EU, claimed Mr Johnson.
"For 30 years, (Corbyn) has been soft and muddle-headed on terror. He has been soft and muddle-headed on defence. He has taken the side of just about every adversary this country has had in my lifetime, from the IRA to Hamas, from Soviet communism to General Galtieri," the Foreign Secretary warned.
"I don't mean to compare our European friends to any of these people, but it is psychologically impossible to imagine him having the grip or the firmness to get the right Brexit deal for this country.
"A Labour negotiating team would arrive in Brussels like a family of herbivores at a watering hole of lions. They would be eaten for breakfast."
Addressing supporters in Stoke-on-Trent, Mrs May said that the loss of six Tory seats in Thursday's poll would mean "Jeremy Corbyn in Downing Street, Diane Abbott looking after our national security, John McDonnell at the Treasury with our economy and the strings being pulled by Nicola Sturgeon".
Warning voters that they could not risk supporting other parties, she appealed: "Give me your backing to lead Britain, give me the authority to speak for Britain, strengthen my hand as I fight for Britain, give me your backing and I will deliver for Britain".
But Liberal Democrat former deputy prime minister Nick Clegg accused Mrs May of a "spectacular failure of leadership" over Brexit by failing to prepare voters for the "huge, excruciatingly difficult, controversial" compromises she will have to make to secure a deal in Brussels.
As a result of her successful drive to woo back Eurosceptic supporters, Mrs May will effectively lead a merged Conservative/Ukip party in the next Parliament, and will go into negotiations with "no room to manoeuvre", he said.
Mr Clegg's successor as leader Tim Farron stood by a prediction that he could double his tally of MPs to 18, telling the Press Association that the Lib Dems "look to be the only opposition party that will make progress in this election".
A Survation poll for ITV1's Good Morning Britain found the Conservative lead over Labour slashed from 17 points to just one over the course of the last month, with the Tories on 41.5% compared with Labour on 40.4%. The Liberal Democrats were on 6% and Ukip on 3%.
Meanwhile, a daily constituency-by-constituency estimate by pollster YouGov suggested Tories could take 304 Commons seats - down 26 from the end of the previous parliament - compared with Labour's 266 (up 37), with the Scottish National Party on 46 (down eight) and the Lib Dems on 12 (up three), denying any party the 323 MPs they need for an absolute majority.
However, there remains wide variation between the findings of different pollsters, with the latest snapshots significantly more favourable to Mr Corbyn's party than other recent surveys.
A Press Association "poll of polls" taking in 11 results from the past week put the Conservatives on 44%, seven points clear of Labour on 37%, with the Liberal Democrats on 8%, Ukip on 4% and the Greens on 2%.