Almost a third of the UK government's most critical no-deal Brexit preparation projects are not on track for completion in time for the scheduled Brexit date of 29 March, according to a new official document.

The previously unseen British cabinet paper warns that many businesses are unprepared for withdrawal without an agreement, which would result in shortages in shops, additional costs to companies and price increases.

The paper also warns that the impact of a no-deal Brexit would be severe in Northern Ireland, where businesses will not have sufficient time to prepares.

The document says disruption to closely-interwoven supply chains and increasing costs could "affect the viability of many businesses across Northern Ireland",

It adds that a no-deal Brexit could lead to some Northern Ireland businesses relocating south of the border.

The document was released in response to an amendment tabled by Independent Group MPs Chuka Umunna and Anna Soubry.

It repeats official analysis suggesting a no-deal could leave the UK economy 6.3%-9% smaller after 15 years than it would otherwise have been, with the worst-hit areas Wales (-8.1%), Scotland (-8.0%), Northern Ireland (-9.1%) and the North East (-10.5%).

The document emerged 31 days ahead of the scheduled date of Brexit, and hours after British Prime Minister Theresa May told MPs that they will be given a chance to vote on delaying EU withdrawal.

The paper indicates that delays and obstacles to cross-Channel trade as a result of no-deal "would not lead to an overall shortage of food in the UK".

But it warns that 30% of the UK's food comes from continental Europe, and Britain is "particularly reliant" at that time of year on supplies of fresh fruit and vegetables via the Channel ports and Tunnel.

"In the absence of other action from government, some food prices are likely to increase, and there is a risk that consumer behaviour could exacerbate, or create, shortages in this scenario," it said.

And it added: "As of February 2019, many businesses in the food supply industry are unprepared for a no-deal scenario."

Following a no-deal Brexit, UK citizens could find themselves subjected to longer waits at the border and exclusion from the use of e-gates for passport checks, the government document said.

And about 240,000 UK companies which trade only with the EU would be caught up in customs processes, with a total administrative burden on business from customs declarations of about £13 billion a year.

The loss of the current "fully free-flowing border" with the EU could result in the flow of goods via Dover and Eurotunnel being "very significantly reduced for months," said the document.

But it added: "French willingness to facilitate cross-border flows means that the government does not currently expect 'day one' disruption to be at the most severe end of its planning assumptions."

The introduction of EU export tariffs, including about 70% on beef, 45% on lamb and 10% on motor vehicles, could have a "very severe" impact on some UK industries, said the document.

It was "impossible to accurately predict the ability of businesses to adapt", but the risk of no-deal is "of major concern" for the car industry, both because of tariffs and disruption to just-in-time supply chains.

Today, MPs in the House of Commons will vote on a number of amendments to a Brexit motion tabled by the government.

Included in those is expected to be the Labour Party's plan for Brexit which supports a permanent customs union with the EU.

If Labour's plan today is defeated - as would be anticipated - then the party leader has pledged to row in behind the idea of a second referendum.

The newly formed group of MPs who defected last week from the Conservatives and Labour has also tabled an amendment relating to another public vote on Brexit.

Additional reporting Fiona Mitchell