John McDonnell has predicted the general election result will prove even more of a “shock” than in 2017, as he signalled the public should vote tactically to oust Boris Johnson.

The shadow chancellor said there would be “interesting results” all over the UK, and for the first time suggested that the electorate would work out how best to vote to defeat Tory candidates.

“Some of you were shocked in the 2017 general election, I think there will be even more shock this time round,” he said.

He said he can’t wait for Friday, when “Jeremy Corbyn turns up on his bicycle, takes off his bicycle clips and walks up to Downing Street”.

Asked by ITV News whether he would urge people to vote tactically, McDonnell replied: “I always urge people to vote Labour, but people will make up their own minds about how their vote will have the maximum effect of preventing a Tory government under Boris Johnson.”

A string of tactical voting websites have urged voters to pick either Labour, SNP or Lib Dem candidates best placed to defeat the Tories in each seat.

In his final speech of the campaign, McDonnell set out his plan for an emergency Budget on February 5, with a promise to start ending austerity through an immediate hike in the minimum wage to £10 an hour and a 5% pay rise for public sector workers.

Pitching directly for Green and Liberal Democrat votes, he stressed that tackling climate change was so urgent that December 12 was the last chance for the UK to do something substantial to save the planet.

“We’ve got no time to lose. If we are going to stop the climate emergency becoming something even worse, any future general election will be too late,” he said.

McDonnell told HuffPost UK that it was vital to tackle the “twin emergency” facing the earth and the health service. “These next five years are going to be key if we are to stand any chance of tackling climate change.

“That’s why I say to our children and grandchildren, if we don’t rise to this challenge, I don’t think they’ll ever forgive us. And they’d be right.”

He stressed the election outcome “will be dependent on turnout” by Labour supporters on polling day, though he admitted that years of austerity and media messaging was having some effect in stopping the public from believing Labour’s radical message.

“Ten years of Tory austerity, of undermining any hope of change, have had their
effect: of limiting people’s horizons and the potential for real change,” he said.

“A decade of austerity, and 40 years of believing the market knows best, have dulled people’s sense of what’s possible, just as they were intended to do.”

Asked why voters appeared not to believe Labour could deliver all its promises, McDonnell said: “What we’ve tried to do is get across to people the scale of the challenges we face and that means we have to scale up our response.

“But yes, Tory lies and some of their friends in the media reiterating those ad nauseum, and at the same time that feeling of 10 years of austerity narrowing people’s horizons, have had some effect.”

Rejecting claims that that sterling would crash because of Labour’s economic plans, McDonnell said “my fear is that the pound will start going up because of our investment plans”.

“When people start talking about a run on the pound, I just ask them to explore the recent history of the pound under a Tory government and suggest to commentators that actually the instability brought about by a combination of incompetent management of the economy, exaggerated claims about what’s potentially available in terms of deals under Brexit, the threat of a no deal and the markets recognising that they have a prime minister whose word cannot be trusted.”

In his speech, the veteran left-winger also warned voters that their grandchildren would ask them in the future “what did you do?” to save the planet and the NHS from Tory neglect.

“When they come to write the history books, and write about when it all began to turn around. When your children or grandchildren ask you: What did you do to end that world of rough sleeping and food banks?

“What did you do to save the NHS and stop the Tories selling it off? What did you do to bring back pride to our town? And to finally wrestle back control from those who had kept it to themselves for so long?

“You can tell them: ‘It all began when we voted Labour, when together we laid the foundations of that new society, foundations so deeply rooted that no Tory could ever tear them up.’”

McDonnell said that Johnson and the Tories “hate” the working classes, and cited his recently highlighted magazine column describing them as “drunk and criminal”.

“Isn’t it interesting that as PM tours round different constituencies, he finds it incredibly different even to mix with people because of the response he’s leaving?

“Arlene Foster has come to a judgement this morning that’s echoed right the way across the country: this is a man who cannot trust…The most important thing now is to make sure people turn out and vote on the day”.