Jeremy Corbyn has insisted Labour is "fighting to win" the General Election as he refused to say if he would quit if the party suffered a defeat at the hands of Theresa May's Tories.
The Labour leader, whose party was making a pitch to low and middle-income families with a pledge that no-one earning less than £80,000 will face personal tax rises, would not be drawn on his future after June 8, saying "we'll see what the result is".
The tax move came as Mrs May announced plans to revamp mental health legislation to end one of the "burning injustices" which she identified in her first speech as Prime Minister last July.
The Tories also attacked Mr Corbyn over his views on security after footage emerged of him calling drone strikes an "obscenity" and calling for the unmanned aircraft - used in the fight against Islamic State terrorists - to be scrapped.
The Labour leader acknowledged the local election results had been a disappointment, with the Tories making sweeping gains as his party suffered losses.
Mr Corbyn told Sky News: "I've been elected to lead this party and I'm very proud to do so. I'm very proud of the increase in our membership and the increase in our party activity.
"Obviously, I am disappointed in the election results on Thursday.
"We're going all out to elect Labour MPs on June 8. After that, we'll see what the result is."
Pressed on his own future, Mr Corbyn said: "I'm not answering any of those questions because we are fighting to win this election to get a Labour government that will deliver for the people of this country the kind of jobs, industries and services that they deserve."
He pointed to the collapse in the Ukip vote as the reason for the Tory success in the local contests.
He said: "I think a lot of Ukip voters probably voted Conservative and I would urge them to think very carefully about what they are voting for.
"Do they want to live in a society where the health service is underfunded, where schools have to have collections from the parents to pay for the teachers and there is a growing housing crisis, or do they want a Labour alternative, which is fair taxation for those who can afford to pay it?"
Mrs May has made the forthcoming Brexit negotiations a key election battleground, arguing she would be better able to get a good deal for the UK than Mr Corbyn.
The Labour leader criticised her tactics, saying: "I wouldn't accuse them (EU officials) of interfering with this country's elections when there is absolutely no evidence whatsoever to suggest they are doing that.
"I wouldn't start negotiations by threatening I might walk away and set up some kind of low tax enterprise on the shores of Europe.
"I would point out to them that we had a referendum, that we've had a decision, that we want to maintain good serious trading relationship with Europe with tariff-free access to the European market."
The Tories stepped up their attack on Mr Corbyn over his stance on defence and security, with the Home Secretary seizing on his 2013 comments about drones.
"They are a key weapon in our battle against radical extremists who are opposed to absolutely every ideal we hold dear," Amber Rudd wrote in the Sunday Telegraph.
"Saying we should scrap drones shows an irresponsible and nonsensical ignorance to the way we protect our country."
Meanwhile, the Liberal Democrats made a pitch for the grey vote by committing to keep the triple-lock protection for the state pension, which would guarantee a boost of at least £772 a year in its value by 2021.
Tim Farron's party risked angering wealthier pensioners, though, with a plan to ditch the winter fuel payment for over-65s with incomes of more than about £45,000 - at a cost of up to £300 a year for 600,000 people.
Former Labour cabinet minister Alan Johnson said the "acid test" for Mr Corbyn is to prove to voters he can be prime minister.
Asked if Labour is facing a battle for its existence, Mr Johnson told Sky News programme Sophy Ridge on Sunday: "Yes, it is, because you lose two elections and that's bad enough.
"To lose three elections on the trot at such a difficult period for our country, that's why Jeremy Corbyn has got to step up to the plate, that's why he's got to show that he can do all the things his supporters believe he can do.
"It is an existential threat to the party."
Shadow foreign secretary Emily Thornberry said Mr Corbyn was "the right leader for this country".
"He has a different leadership style to the leadership styles we have had in the past, he does tend to work much more in teams than perhaps some of our other leaders have done, and that's a strength," she told BBC Radio 4's The World This Weekend.