As Britain prepares to go to the polls in a general election in mere days, prime minister Boris Johnson has launched has Conservative party manifesto with a promise to "get Brexit done".

In the document published at the weekend, Mr Johnson insisted he will not extend the 11-month transition period that kicks in if the UK leaves the European Union as anticipated on January 31st 2020, aiming instead to negotiate a trade deal with Europe in double-quick time.

It has also emerged that if the Conservatives win a majority in the election, MPs will vote on Mr Johnson's Brexit deal before Christmas in a bid to ensure it is approved by the start of next year.

However, Britain's former envoy to the EU Sir Ivan Rogers said at a university lecture that Mr Johnson is sowing the seeds of "the biggest crisis of Brexit to date" by taking this stance.

He accepted the UK may be able to get what he called a "quick and dirty" trade deal by the end of 2020, but warned this would be at the expense of the UK services industry and would also give the EU leverage when it came to fishing rights in British waters.

"It ultimately lands us with a poor and deteriorating relationship on multiple things that really matter, economically and strategically," Sir Ivan said.

Meanwhile, leader of the opposition Jeremy Corbyn has said he intends to adopt a "neutral stance" should Labour win the general election and enact a fresh Brexit referendum.

Speaking at a question time event, he said this would allow him, as prime minister, to "credibly carry out the result of that to bring our communities and country together".

Mr Corbyn also confirmed Labour would aim to negotiate a softer Brexit deal within three months, with a referendum three months after that.

This has been criticised as an attempt by Mr Corbyn to avoid backing the side that goes against popular opinion, which could ultimately end in his having to resign as David Cameron did.

Sir Ivan was equally scathing about Mr Corbyn's position, commenting that it "frankly deserves the Brussels eye-rolling it duly gets" and reflected denial by remainers who wanted to turn back the clock on the original referendum that triggered Article 50.

Elsewhere, British chancellor of the exchequer Sajid Javid has failed to say whether or not he plans to set aside money to cover the country should a free trade agreement fail to be agreed with the EU by the end of 2020. 

His predecessor Philip Hammond was known to have budgeted £27 billion to prepare for disruption to transport, food and medicine provision, but this has since been reallocated.

In an interview with Sky News, Mr Javid said he has "no doubt" that a deal can be done quickly after January 31st 2020 if Mr Johnson wins the general election.

Meanwhile, the IHS Markit/CIPS flash index of business activity has shown Britain's private sector companies suffered their sharpest decline in activity this month since the original EU referendum.

This contraction in November 2019 orders and production was attributed to Brexit-related uncertainty impacting upon domestic and overseas customers.