Nigel Farage has announced he will once again begin actively campaigning in British politics against Theresa May’s “fraudulent” plans for Brexit.

The ex-Ukip leader said it was necessary as a result of the “deceit and treachery” of politicians and senior figures in British society in their approach to European Union withdrawal.

In particular he singled out an exclusive report in The Independent with warnings from the British Medical Association that a no-deal Brexit would be a “catastrophe” for the NHS.

His re-entry into politics comes as The Independent drives forward with its Final Say campaign for a new referendum on the outcome of Brexit – with more than 650,000 people now having signed a petition.

Pressure is intensifying on the government ahead of Brexit day in March next year, with Theresa May’s own MPs even drawing up alternative proposals to the prime minister’s plan, which is receiving meagre public support.

Writing in the Daily Telegraph, Mr Farage claimed people had stopped him in the street to ask when he was returning, adding in his article: “Well, now you have your answer. I’m back.”

He said: “It is now beyond doubt that the political class in Westminster and many of their media allies do not accept the EU referendum result.

“It is equally clear to me that, unless challenged, these anti-democrats will succeed in frustrating the result.

“Well, I’ve had enough of their lies, deceit and treachery. The time has come to teach them a lesson – one that they will never forget.”

He said he had decided to commit himself to the Leave Means Leave campaign, which is set for a relaunch, following discussions with its founders, businessmen Richard Tice and John Longworth.

In his piece, Mr Farage wrote: “To make matters worse we are subject to a daily stream of negative to beat us into submission.

“The latest example was the British Medical Association suggesting that a no-deal Brexit would lead to huge numbers of people dying.

“This baseless claim proves project fear is thriving. We need leadership.”

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Mr Farage was referring to an article in The Independent in which the BMA said a failure to secure a deal could increase the risk of a Europe-wide pandemic.

The doctors union warned in a new briefing paper that the UK’s ability to coordinate responses to emerging threats, such as the current outbreak of measles or seasonal flu, will be seriously undermined, making it harder to stop infections spreading across borders.

This is the most extreme form of project fear yet, these people are an absolute disgrace. https://t.co/9J4DJCRQsC — Nigel Farage (@Nigel_Farage) August 16, 2018

With the UK government admitting it is stockpiling medicines in the event of a no-deal scenario, the BMA said it is proof that the devastating impact of Brexit on the nation’s health has been neglected.

Mr Farage’s return is another potential headache for Ms May who is already facing bitter opposition to her Chequers proposals from a significant section of the Conservative Party.

In his article, Mr Farage said Ms May’s plan would do nothing to enable the UK to take back control of its borders and fishing rights and to strike free trade deals around the world for “many years to come”.

He said: “Theresa the Appeaser has produced a set of ideas that are nothing more than a cowardly sellout. With all this in mind, now is the time for action,” he said.

The Brexit-backing European Research Group of Tory MPs, led by Jacob Rees-Mogg, is already preparing an alternative set of plans – highlighting benefits of a no-deal Brexit – from the prime minister’s. They are due to be published next month.

Former foreign secretary Boris Johnson also appears to be positioning himself as an alternative leader to Ms May, with this year’s Conservative conference set to be a flash point for her leadership.

In a significant development in the drive for a new referendum, The Independent and the People’s Vote campaigns are joining forces for a mass march through central London on 20 October.

The alliance will see the two organisations mobilise activists and media across the country to capture the growing tide of opinion that a further referendum on Brexit must be held.

An exclusive poll carried out by BMG Research this week found that 48 per cent of the public would now back a vote on any deal struck between the UK and the EU – up from 44 per cent just four weeks ago.

Just 24 per cent opposed the idea, down three percentage points over the same period. Only 14 per cent of the 1,500 people surveyed supported Ms May’s Chequers deal, given a choice.