The Tories should make tearing up the Northern Ireland Protocol a general election campaign promise unless Brussels caves to British demands to renegotiate the treaty, Lord Frost has said.

The former Brexit negotiator said the EU had to recognise that the protocol was “always temporary” and that it was “not realistic” for the Irish Sea border to last forever.

The protocol keeps Northern Ireland subject to some EU laws and introduces customs checks on British goods entering the province to prevent a hard Irish border after Brexit.

Brussels has repeatedly said the treaty will not be renegotiated, but has offered to cut the number of checks faced by British goods entering Northern Ireland. 

“If the protocol isn’t redone then the poison between us will remain,” Lord Frost said in a speech in non-EU member Switzerland, as he called for the two sides to “move on” from Brexit. 

Threat to trigger Article 16

Unless the EU folds, Lord Frost said, the Government would trigger Article 16 of the protocol and unilaterally suspend parts of the agreement. The EU has warned it could cancel its free trade agreement in retaliation. 

If Brussels agreed to the UK demands, the Government could take Article 16 off the table, he said. It could also offer improved foreign policy and security cooperation and increased mobility for musicians, artists and students between the UK and EU in return.  

The Northern Ireland Assembly will hold its first “consent vote” on the protocol in 2024, which is also the likely year of the next general election.

The Government should be prepared to campaign for a no vote in the Assembly and could even call fresh Stormont elections ahead of the vote, Lord Frost said.

Making ending the protocol a manifesto promise ahead of the general election would prevent the move being blocked by the House of Lords, he added. 

The UK could use dispute measures in the Brexit agreements and “once again raise the spectre of us trading globally on something closer to WTO terms”, Lord Frost said. 

Lord Frost resigned from the Government in December last year. Since then, EU negotiations have been led by Liz Truss, the Foreign Secretary, who has said Article 16 will not be used during the Ukraine crisis.