Jeremy Corbyn has said he feels confident as the election campaign enters its final days, standing by Labour’s attacking strategy despite fears among candidates in defensive seats that they have been left exposed.

In a wide-ranging interview, Corbyn said he thought Labour had “got the message out” across the six-week campaign and rejected calls to encourage tactical voting to defeat Boris Johnson.

“I’m feeling very happy, very confident,” he told the Guardian en route from a rally in Bristol city centre to a noisy public meeting at football club Forest Green Rovers, near Stroud.

“We’ve got the message out, and we will continue to make sure it gets out over these last few days. And fundamentally, the choice is: do you have hope and investment for the future, or do you go down the market road with the Tories?”

Asked whether it had been the right approach to pour activists and resources into winning Tory-held seats, he said: “I’ve been to 60-something seats already. Most of them are offensive marginals, where we’re trying to win them. I haven’t been to that many places that we’re defending, but I want to support colleagues who’ve done a great job – so I went to Crewe to support Laura Smith, we’re going to Stroud to support David Drew. But most of the places we’ve been to are places we’re going to win.”

He acknowledged concerns about what he called Labour’s “comprehensive” manifesto, which some candidates have complained is so packed with consumer giveaways that many voters are baffled.

“As the manifesto was being put together, I was one who was always cautious about an overlong manifesto,” he said. But he pointed to the “enthusiasm of people to write it” and the need to set out Labour’s policies in detail on issues including the environment. “I think it’s right to do that,” he added.

With just two more days of campaigning to go, Boris Johnson’s party retains a comfortable lead in most polls, despite questions over whether Johnson’s “get Brexit done” slogan dramatically underplays the challenges looming in 2020.

Labour leader Jeremy Corbyn at a rally held at Forest Green Rovers’ ground. Photograph: Sean Smith/The Guardian

Labour’s most likely route to government on Friday is with the cooperation of other, smaller parties. But Corbyn rejected the idea that voters should vote tactically for the best-placed candidate to beat the Conservatives. Asked about it, he simply repeated, “I would encourage people to vote Labour. I would encourage people to vote Labour.”

Challenged about whether he is good at reaching out beyond Labour’s loyal base, to win over ex-Tory voters, Corbyn said: “I do my best to. I’ve been a member of parliament for a very long time, I’ve travelled around this country for years, and I’ve got a love and an understanding of this country and the brilliant bits of local history and diversity that we have. And I love it.”

Labour’s appeal during the campaign has sometimes appeared to be a moral one – to voters’ social responsibility, more than to their pockets. But Corbyn insisted that the party’s message was altruistic as well as practical. “It’s both.”

He added: “I meet people in reasonable jobs, in middle age, who thought life was getting stable for them and they were doing OK, and suddenly in their late 40s and 50s they are having to borrow money to put their kids through uni, or watch their kids get into debt. Or they’re having to give up work to look after elderly parents who need social care. They’re actually paying the price for austerity as much as those children living in poverty.”

Asked how he would appeal to leave voters, Corbyn was keen to highlight the fact that Labour’s new Brexit deal, which he has promised to secure within three months, would be negotiated by a “balanced” team.

That suggests Sir Keir Starmer, who has been shadow Brexit secretary for three years, would find himself accompanied by at least one leave supporter, perhaps from a seat outside London.

Some of Corbyn’s supporters have complained that the party’s stance has skewed too much towards remain in the past 12 months, in a way that has prejudiced its chances in seats in the Midlands and the north.

Corbyn said: “I say to those people who voted leave, I’m sure you voted leave for many, many reasons, but I doubt you voted leave to see our manufacturing industry decimated or the protections and rights we have at work damaged. We’ll put that choice before the people of this country.”

He refused to engage with questions about whether he would step down on Friday if Labour fails to deprive Johnson of a majority. “We’re intending to win on Thursday, so the question doesn’t arise,” he said.

Many party insiders are openly speculating about who could succeed Corbyn. Several potential leftwing successors, including Rebecca Long-Bailey, Angela Rayner and Laura Pidcock, have taken prominent roles in the campaign.

Other possible candidates who have embraced a remain stance, including Starmer and Emily Thornberry, have been allowed little presence, amid fears among Labour strategists of Brexit voters being deterred.

One approach mooted at the party’s conference in September was that Corbyn’s old ally John McDonnell could take over as an interim leader, after a rule change made by Labour’s ruling national executive committee that was overshadowed at the time by the failed putsch against Tom Watson.

A contest for the deputy leadership is already looming in the coming months, after Watson announced that he would not stand again for parliament. His former seat, West Bromwich East, is among those that Labour fears could be at risk on Thursday.