Labour is to present its most radical manifesto ever in the coming days with plans to introduce a universal basic income and drastic measures to tackle the climate emergency, John McDonnell has said.

In an interview with The Independent, the shadow chancellor insisted his party will pilot the contentious welfare scheme and suggested Heathrow expansion will be blocked as the party aims to achieve net-zero emissions by the 2030s.

Claiming Labour will “turn around” its poll ratings, Mr McDonnell also said he would hold a Budget within weeks if his longtime ally Jeremy Corbyn becomes prime minister after the first December election in nearly a century.

His comments come ahead of a crucial summit of Labour’s senior figures, known as the “Clause V meeting”, to sign off the party’s blueprint for government. The draft is currently being finalised by some of Mr Corbyn’s top advisers.

The shadow chancellor insisted it would “more radical” than Labour’s 2017 manifesto – a document the party credited for reversing its dismal prospects and depriving Theresa May’s Conservatives of a majority in the House of Commons.

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On the issue of a universal basic income, Mr McDonnell, who has long been a proponent of the policy, said he was looking at including “at least one pilot” in Labour’s blueprint for government.

There are many variations of basic income, but the concept generally involves overhauling the welfare state by scrapping means-tested benefits and replacing them with weekly or monthly payments to all citizens.

Pressed on whether it was going to be in Labour’s new manifesto he replied: “Yeah. Well, the Clause V meeting is what determines the final manifesto. I’ll be submitting into the draft for consideration by Clause V that we have a pilot.”

“We’ve had bids from Liverpool, Sheffield, a couple of other places,” he added. “Sheffield have really made a big pitch for the UBI, a pilot, but there are a few other places as well. They are the ones really that are willing to look at how they can tackle poverty.”

A report presented to Mr McDonnell earlier this year by Professor Guy Standing, an economic adviser to the shadow Treasury team, highlighted various models a government could use in a pilot scheme of basic income. One included providing every adult in a selected community with £100, and a further £50 for each child per week. Additional benefits would be put in place for those with disabilities.

Professor Standing argued a basic income is needed to tackle economic insecurity, debt and stress, and the threat posed by artificial intelligence with considerable numbers of jobs disappearing in the coming decades.

Mr McDonnell also made clear the climate crisis will feature prominently throughout the manifesto. “We’ve got to recognise there’s an existential threat to our planet,” he said.

He reiterated his longstanding opposition to a third runway at Heathrow airport, and claimed it does not pass Labour’s environmental, economic and social tests.

“I don’t think it qualifies under those criteria,” he added. “So I can’t see it going ahead. But we’ve got the legal challenge at the moment. We’ve got the stop-Heathrow-expansion general meeting. We’re hoping the decision from the courts will rule it out anyway.”

Pressed on whether private jets should be banned in the UK – something advocated by the left-wing think tank Common Wealth earlier this week – Mr McDonnell replied: “Yes”.

He continued: “I think we’re going to have to take action against them. We can’t go on like this. If you look at the figures, about 40 per cent of them are being flown empty. And they are simply being flown to locate them where their owners are.”

The report found there were 128,000 private jet flights between the UK and European airports last years – around 6 per cent of British air traffic. It noted that private jets “were more amenable to rapid electrification” as they tended to be small and relatively light.

On Brexit, the manifesto is widely expected to reiterate the policy decided at Labour’s annual conference: to negotiate a new deal with the EU within three months and then hold a Final Say referendum, with Remain as an option. The party will decide how to campaign at a special Brexit conference of members, but it is unclear whether Mr Corbyn will remain neutral.

“Quite rationally, he’ll say, ‘wait until you see the actual deal that has been done and they can make a decision’,” Mr McDonnell said. “He’ll make a decision about what attitude he’ll strike in any campaign.”

The shadow chancellor also ridiculed the suggestion by Channel 4’s Dispatches programme that he met with Mr Corbyn and Diane Abbott, the shadow home secretary, at the Labour leader’s allotment in north London.

It was reported they agreed in the summer that the party should move to a more unequivocal Remain position, but Mr Corbyn was persuaded not to do so by his director of strategy and communications, Seumas Milne.

“Here’s the irony of it all,” Mr McDonnell said. “I’ve never been on Jeremy’s allotment. He phones me from the allotment and says, ‘I’m doing this at the moment,’ and he’ll send me a photograph of his latest crop.

“I’ve actually never been on the allotment. He’s been in my garden and criticised my garden, so I don’t invite him anymore.”

Mr McDonnell, who is chairing Labour’s election coordinating committee, also rejected reports that there had been a strain in relations between himself and the Labour leader in recent months, insisting it was “media rubbish” designed to “divide and rule”.

“There’s a hardy perennial every autumn that I’m either launching a coup or I’m imprisoning him,” he added. “In one newspaper they had the same in the same week. It’s rubbish. We talk everyday, several times a day on different matters.”

Asked whether he was the “real leader” of the party – a suggestion made by commentators in recent weeks – he said: “I usually use language that may not be appropriate for your newspaper because it’s rubbish, it’s rubbish.

“They have no understanding of the relationship Jeremy and I have. We’ve worked together for over 40 years.”

If Mr Corbyn were elected prime minister, Mr McDonnell said he would not move into 11 Downing Street – the traditional residence of the chancellor of the exchequer – and rather stay at his home in his Hayes and Harlington constituency.

He will hold his first Budget within “six to eight weeks”, and has already been holding a series of meetings with Sir Tom Scholar, the most senior civil servant at the Treasury, to outline his plans for a complete overhaul of the department.

A major part of his proposals includes what he described as “the shift of the pound” – relocating a significant proportion of the Treasury to his hometown of Liverpool