EU and UK officials privately concede they do not know how Article 16 would play out because it is an entirely new mechanism without any international precedent.

The Northern Ireland Protocol keeps the country in the EU’s customs territory for goods and follows EU pharmaceutical regulations to avoid a hard Irish border.

This creates the risk of medicines being authorised or rejected in Northern Ireland but not in the rest of the UK because there will be separate regulators once a grace period in the protocol expires at the end of the year.

The EU has offered to change its laws to allow the continued supply of existing cheaper generic drugs, which have already been approved by the UK regulator.

But new medicines would not be allowed to be sold in Northern Ireland unless they are approved by the European Medicines Agency or a national supervisor in the EU, even if they are authorised by the British Medicines and Healthcare products Regulatory Agency (MHRA).

British negotiators want Brussels to agree that Northern Ireland can get new life-saving cancer drugs and antiviral Covid medicines if they are approved by the MHRA. 

The Government fears companies could forgo the relatively small Northern Irish market rather than applying for market authorisation twice. Differing rules could mean extra labels or bespoke Northern Irish boxes for medicines, which would not be economically viable for smaller firms with tight margins.

Lord Frost has suggested removing medicines from the scope of the protocol and having them supervised exclusively by the UK. Britain could settle on a compromise that allows both new, old and veterinary medicines approved by the UK regulatory body to be sold in Northern Ireland.