The UK would waive checks at the Irish border checks and scrap tariffs on 87% of goods coming to the UK under a no-deal Brexit, the government has confirmed.

A senior UK government source said the measures in Northern Ireland would have a detrimental impact on Northern Irish farms and businesses.

Without tariffs on imports, many British manufacturers and businesses would struggle to compete with cheap imports, and Britain would lose leverage to persuade other countries to reduce tariffs on goods arriving in the country.

The news comes as a majority of MPs prepares to reject a no-deal Brexit on Wednesday evening.

LONDON — The UK would refuse to introduce any Irish border checks and scrap 87% of tariffs on imported goods to the UK if it leaves the EU without a deal, officials have confirmed.

Theresa May's government published explosive details of the tariff cuts and its Irish border plans after Theresa May’s Brexit deal was defeated heavily in parliament on Tuesday, significantly increasing the likelihood of no deal.

Downing Street would take unilateral measures to maintain an open Irish border by waiving new checks or controls on goods moving from Ireland to Northern Ireland, including no customs declarations for normal goods.

There are currently no checks between the two countries because both are members of the European Union's customs union and single market.

The government would replace checks with an "honesty box" policy where businesses are expected to self-report the movement of goods. There would also be an online payment system for VAT payments.

A government source said the measures would have a detrimental impact on Northern Irish farms and businesses, which would struggle to compete with a flood of cheap imports, but said it was the only way to avoid a hard border in Ireland.

The government has consistently said it will try to avoid the emergence of new checks on the Irish border in order to respect the terms of the Good Friday Agreement. But it has not released policy details of the politically sensitive issue until now.

Karen Bradley, the Northern Ireland secretary, said: "These arrangements can only be temporary and short-term."

It is still unclear whether the Irish government will implement the same policy on its side of the border to ensure that no new checks emerge.

The news comes as MPs prepare to vote to accept or reject the prospect of a no-deal Brexit in parliament on Wednesday evening. A majority of MPs is expected to vote against no deal, which will trigger another vote on Thursday evening on whether parliament wishes to delay Brexit.

Tariff plans 'a sledgehammer' for British economy

A coach moves across the border between Northern Ireland and Ireland Getty

The government also said that it would scrap tariffs for a total of 87% of imports to the UK, a system it said would "minimise costs to businesses."

The CBI, which represents 190,000 UK firms, said the plans would be destructive for the economy.

"What we are hearing is the biggest change in terms of trade this country has faced since the mid-19th century being imposed on this country with no consultation with business, no time to prepare," said CBI chief Carolyn Fairbairn.

"This is a sledgehammer for our economy."

Tariffs would still apply to certain commercially sensitive sectors, including meat and automotive parts.

Britain currently has tariff-free access to EU markets and enjoys EU trade deals with other countries, all of which will end once the UK leaves. Exports from the UK will still automatically face new tariffs even if the UK unilaterally cancels most scraps tariffs on inbound goods.

Without tariffs on imports, many British manufacturers and businesses would struggle to compete with cheap imports, and Britain would lose leverage to persuade other countries to reduce tariffs on goods coming to the country, which would have a further detrimental impact on British firms.

Trade minister George Hollingberry said: "If we leave without a deal, we will set the majority of our import tariffs to zero, whilst maintaining tariffs for the most sensitive industries."