A group of senior congressmen have told Boris Johnson to scrap his Brexit plans or abandon hopes of a trade deal with the US

• Boris Johnson is under growing pressure from the US to drop his Brexit plans.
• The UK government has announced that it intends to give itself the power to break the deal it signed with the EU last year.
• Last week, House Speaker Nancy Pelosi said there was "absolutely no chance" of a UK-US free trade deal if the UK prime minister went ahead with the plan, which has outraged Brussels and MPs in London.
• Now four senior congressmen have urged Johnson to bin the plan in a letter to the prime minister.
• It says they were "disturbed" by the plan and its risk to peace and warned it risked the peace process in Northern Ireland.
• It was signed by House committee chairs Eliot Engel, Richard Neal and William Keating, plus senior Republican congressman Peter King.

Four senior congressmen have written to Boris Johnson warning him that there will be no post-Brexit free trade agreement between the US and the UK if he does not abandon his plan to rewrite his Brexit deal with theEU.

House Speaker Nancy Pelosi last week told the UK prime minister there would be "absolutely no chance" of a post-Brexit trade deal if he went ahead with his contentious plan.

Now the congressmen, including three committee chairs and a prominent Republican, reiterated the warning in a letter to Johnson which says that they were "disturbed" by his government's decision to break international law.

On Tuesday Foreign Affairs Committee chair Eliot Engel, Ways and Means Committee chair Richard Neal, subcommittee on European affairs chair William Keating, and Republican congressman Peter King, wrote to Johnson urging him to abandon his plan or risk torpedoing any prospect of a post-Brexit free trade deal with the US.

In a letter to the UK prime minister, they said they have "grave concern over recent reports that you may be working on legislation or other efforts that would like invalidate or override the Northern Ireland protocol of last year's European Union-United Kingdom Withdrawal Agreement."

The quartet said the US played a key role in brokering peace in Northern Ireland, and "it is for the reasons that we were so disturbed by the reports about your government's efforts to undermine the Northern Ireland protocol of the Withdrawal Agreement that, if true, could have disastrous consequences for the Good Friday Agreement and broader process to maintain peace on the island of Ireland."

They echoed Pelosi's warnings, telling Prime Minister Johnson "many in the United States Congress consider the issue of the Good Friday Agreement and the potential US-UK Free Trade Agreement to be inextricably linked" and "if these reported plans were to go forward, it would be difficult to see how these conditions [for Congress to approve a trade deal] could be met."

They added: "We therefore urge you to abandon any and all legally questionable and unfair efforts to flout the Northern Ireland protocol of the Withdrawal Agreement and look to ensure that Brexit negotiations do undermine the decades of progress to bring peace to Northern Ireland and future options for the bilateral relationship between our two countries."

In an interview last week, congressman Neal said Johnson's plan to rewrite elements of the Northern Ireland protocol was "a violation... of the good faith that we all entered into in negotiations that brought about this remarkable achievement called the Good Friday Agreement."

Johnson's UK government has caused consternation in the UK, Brussels, and Washington after revealing an explosive plan to unilaterally determine elements of Northern Ireland's trade with Great Britain from January next year.

Details of how the Northern Ireland protocol, agreed as part of Brexit withdrawal talks last year, will work in practice are being negotiated by UK and EU officials. Brandon Lewis, the UK Secretary of State of Northern Ireland, admitted last week that the UK's plan to unilaterally implement its own reading of the protocol would break international law.

Several members of Parliament of Johnson's Conservative party, including former UK prime minister Theresa May, publicly criticised the move and dozens are expected to vote against it next week if he doesn't change course. Jonathan Jones quit as the head of the UK government's legal department last week in protest against the plan.

The Northern Ireland protocol of the Brexit Withdrawal Agreement states that the province will continue to follow EU trading rules in order to avoid a controversial hard border with the Republic of Ireland.

However, Johnson's UK government intends to use two pieces of legislation – the International Market Bill and Finance Bill — to effectively disapply parts of the Northern Ireland protocol. The EU reacted furiously last week, warning the UK that it would consider legal action if it didn't scrap the plan by the end of the month.

Downing Street is this week in talks with Conservative Members of the UK Parliament about a potential compromise in order to prevent a backbench rebellion when the House of Commons votes on the legislation next week.