Boris Johnson will begin a blitz of Labour’s heartlands in a bid to convince Leave voters that Jeremy Corbyn’s Brexit position is akin to a “great betrayal”.

The Prime Minister will spend the three days before polls open targeting voters in traditional Labour strongholds, which his party views as key to securing a Conservative majority.

In a bid to help crack the so-called “red wall” of Labour seats across the North of England, the Conservative Party leader will spend Monday in the Leave-voting regions of the Humber and Wearside.

The PM will blast Mr Corbyn for sticking “two fingers up to the public” on Brexit during his tour of Labour seats.

Places like Grimsby have not been held by a Tory MPs since the Second World War.

In Sunderland – where Mr Johnson said Brexit’s “roar” was heard for the first time on referendum night after the city’s quick count showed a huge swing towards Leave – the PM will tell North East voters that it is Labour that has “let you down most of all” on Brexit.

“It’s been the great betrayal, orchestrated from Islington by politicians who sneer at your values and ignore your votes,” he will say.

It comes as the former Vote Leave figurehead’s pledges on Brexit were brought into question after a second leak pored doubt on the country’s ability to be ready to exit the European Union within a year.

The PM will tell voters on Wearside that there is only “three days to get Brexit done” – but a leaked Government document suggests delivering customs arrangements related to Northern Ireland’s post-Brexit relationship with Britain by December 2020 would be a “major challenge”.

The ex-foreign secretary has consistently vowed to take the UK out of the EU by January 31 and then finalise a trade deal with Brussels within 11 months to meet the transition period deadline.

Arrangements would also need to be signed off that allow Northern Ireland to continue to follow Brussels and Dublin rules on the trade of goods to ensure there is no hard border.

But a Whitehall report seen by the Financial Times highlights the difficultly involved for the Government in bringing in the infrastructure in time for the UK to leave when the PM has pledged.

A Department for Exiting the European Union document, according to the FT, states that: “Delivery of the required infrastructure, associated systems, and staffing to implement the requirements of the (Northern Ireland) protocol by December 2020 represents a major strategic, political and operational challenge.”

Last week, Labour released a leaked Treasury report that concluded customs checks and possibly even tariffs could be required on goods travelling in both directions between Northern Ireland and Great Britain.

But Mr Johnson told Sky News’ Sophy Ridge On Sunday programme that the report was “wrong” and added that the six counties would have “unfettered access” to the UK market.

Labour, in a further digging exercise through Mr Johnson’s past writings, have unearthed further controversial comments made by the former London mayor.

Party officials had previously discovered an article from 1995 in which the ex-journalist was disparaging about single mothers and he has been criticised for describing Muslim women wearing burqas as looking like “letterboxes” in a column.

According to comments found by Labour in articles in the Daily Telegraph and Spectator magazine, Mr Johnson said it was “right” that Tories should wish its leadership to “speak up more strongly against…gays in the military”.

He is also alleged to have complained that police were “deployed in desperate attempts to catch paedophiles in ancient public schools”.

Shadow chancellor John McDonnell said: “The more we learn, the worse it gets. As well as being a danger to our NHS and a pathological liar, it is clear that Boris Johnson is a deeply unpleasant individual.”

The PM also came in for criticism during a heated televised Channel 4 debate on Sunday evening after both the Tories and Brexit Party ducked the Britain Decides: Everything But Brexit Debate.

Presenter Cathy Newman read out Tory responses to some of the non-Brexit related questions but the governing party’s decision to skip the debate came in for stern words.