However, a concession allowing “national identity goods” such as sausages to enter Northern Ireland – despite EU rules restricting chilled meats from non-EU countries – was dismissed by UK sources as only addressing a “tiny” part of the problem.

In the event that the EU refuses “significant changes” both to remove trade barriers between Britain and Northern Ireland and eliminate the role of the ECJ, Number 10 is planning to trigger Article 16 of the Protocol in order to unilaterally suspend parts of the agreement.

However, senior figures believe the Government may be required to pass legislation enacting the move – setting up a potentially major clash with the House of Lords.

For years, the Conservatives have been heavily outnumbered by Labour and Liberal Democrat peers, although Tory figures said the party was now significantly closer to being able to win votes in the Lords partly because of a slew of appointments under Mr Johnson’s premiership.

One senior MP urged Mr Johnson to continue appointing new peers to increase the party’s presence in the Lords. The MP even claimed that Dominic Raab, the Lord Chancellor, and Jacob Rees-Mogg, the Leader of the Commons and Lord President of the Council, could use archaic rights to vote in the Lords if a division came down to a knife edge.

Tory whips are more relaxed about the prospects of passing Article 16 legislation in the Commons, where Mr Johnson enjoys a working majority of 81.

The Conservatives’ 2019 manifesto pledged to “ensure that Northern Ireland’s businesses and producers enjoy unfettered access to the rest of the UK”, which the Prime Minister has said is under threat from the implementation of the Protocol.

Writing in The Telegraph, Sir Jeffrey Donaldson, the leader of the Democratic Unionist Party, said the Prime Minister agreed with his view that the UK should trigger Article 16 “if the EU does not step up and restore Northern Ireland’s place within the UK internal market”.

If Mr Johnson opts to trigger Article 16 without legislation, he is expected to face a legal challenge similar to the cases mounted by the anti-Brexit campaigner Gina Miller in 2017 and 2019, which could force his hand.

The Northern Ireland Protocol is the part of the UK’s exit deal from the EU which covers the goods trade on the island of Ireland. Mr Johnson and Lord Frost have demanded changes to the document on the basis that the EU’s “rigid” application of its rules is causing significant disruption to businesses and risks “economic damage” in Northern Ireland.