Boris Johnson has apologised to the Tory members who elected him leader for failing on his "do-or-die" promise to implement Brexit by Halloween.
The Prime Minister said he feels "deep regret" over missing the former deadline, which he was compelled to extend to the end of January.
With the EU departure the overwhelming focal point of the election campaign, Brexit Party leader Nigel Farage ruled out making an eighth bid to become an MP in the December 12 vote.
Meanwhile, the main political parties clashed over policies on the climate crisis, the welfare state and the EU.
So adamant was the PM that he would meet the last Brexit deadline, he said he would rather be "dead in a ditch" than miss it. That date passed on Thursday.
In an interview with Sky's Ridge on Sunday, he was told he needed to take responsibility and could not just blame other people.
"Well, I do. I do and I'm deeply, deeply disappointed," the PM replied.
Pushed on whether he would apologise to Tory members who supported him, Mr Johnson replied: "Of course, of course.
"It's a matter of ... it's a matter of deep regret."
Mr Johnson also said he can see "no reason whatsoever" about why the UK should extend the Brexit transition period beyond December 2020, adding: "If you get the right Parliament anything's possible."
Whether the Brexit Party succeeds in getting any MPs elected or not, Tories fear the party could play a major role in splitting the Leave vote.
The Conservatives have rejected his offer of an electoral pact and on Sunday Mr Farage continued with his threat to stand candidates in around 600 seats.
But he ruled out standing himself, telling the BBC's Andrew Marr Show: "I've thought very hard about this - how do I serve the cause of Brexit best, because that's what I'm doing this for.
"Not for a career, I don't want to be in politics for the rest of my life.
"Do I find a seat to try get myself into parliament or do I serve the cause better traversing the length and breadth of the United Kingdom supporting 600 candidates, and I've decided the latter course is the right one."
In a move likely to rile the proponent of a no-deal departure, senior Treasury minister Rishi Sunak failed to deny suggestions the threat was being removed from the Tory manifesto.
On the opposite side of the Brexit spectrum, the Lib Dems were not ruling out forming a Remain electoral alliance in up to 60 seats to boost the chances of preventing a Conservative majority.
Talks have been under way between the unequivocally pro-EU parties of the Lib Dems, Plaid Cymru and the Greens to boost the chances of electing anti-Brexit MPs.
Lib Dem leader Jo Swinson told Sky: "I wouldn't necessarily assume that the numbers are accurate.
"I think it's fair to say that in the vast majority of constituencies the party of Remain that is going to be best-placed to win that seat will be the Liberal Democrats."
Labour's Rebecca Long-Bailey confirmed that the party could campaign to leave the EU in a second referendum if it secures a strong enough new Brexit deal from Brussels.
"Ultimately underpinning our final decision is how good that deal is," the shadow business secretary told Sky.
In election pledges, the Government announced it would in April end the benefits freeze imposed by Tory former chancellor George Osborne.
Labour said "nobody will be fooled" by the "cynically-timed announcement", while campaigners were also critical.
Polly Neate, chief executive of homelessness charity Shelter, said: "While the Government may have finally called time on its benefits freeze, the proposed rise in support is so tiny it won't make a dent in the damage already done."
Jeremy Corbyn was proposing a move to upgrade almost every home in the UK with energy-saving measures to tackle the climate crisis and bring down household bills.
Labour says work to install loft insulation, double glazing and renewable and low carbon technologies in nearly 27 million homes by 2030 would create 450,000 jobs and cost the government £60 billion.