In protest against the Brexit rules agreed with the EU for Northern Ireland, the most important party on the Protestant Unionist side is refusing to work in the parliament of the British part of the country.

The Democratic Unionist Party (DUP) will neither vote for a speaker nor put forward its own candidate in the first session of the newly elected National Assembly on Friday, party leader Jeffrey Donaldson told the Belfast Telegraph newspaper. Parliament is thus unable to work.

As an ultimatum, the DUP demands that the British government repeal the so-called Northern Ireland Protocol, which it had agreed with the EU in the wake of Brexit. The regulation is intended to prevent controls at the border to the EU member Republic of Ireland and thus new conflicts in the former civil war region.

In return, however, a customs border has been created between Northern Ireland and the rest of the United Kingdom. The British government and supporters of the Union like the DUP therefore fear alienation from London.

Donaldson emphasized that the party is consistently implementing its election promises. He said the protocol jeopardizes security and stability in Northern Ireland and all the agreements that have been reached over the past 25 years.

The UK government has given the EU an ultimatum to agree to changes to the treaty. Otherwise, London wants to end the regulation unilaterally. In that case, a trade war could loom. The EU had announced that it would question the entire Brexit treaty.