The border between Northern Ireland and Ireland
Tractors drive past an exit sign and a road sign for Belfast on the border between Northern Ireland and Ireland, in Jonesborough, Northern Ireland, May 19, 2022.

The European Commission is willing to negotiate trading arrangements for Northern Ireland with Britain, but only if talks are constructive and do not resume with an outcome already set by London, a top EU official said on Wednesday.

"Our doors are open for negotiations but it has to be constructive negotiations and it cannot be done in a way that we negotiate but the result is given in advance," Commission Vice President Maros Sefcovic told a news conference in Brussels.

Sefcovic delivered a speech in London later on Wednesday, two days after legislation allowing Britain to scrap some of the rules on post-Brexit Northern Ireland trade passed the first of many parliamentary tests.

Sefcovic told his British audience that the UK bill was not only a violation of international law but would lead to "constant uncertainty".

"Put simply: it would not work," he said, with British ministers able to change the rules on a whim and a dual regulatory regime burying businesses under bureaucracy.

The British government also had to be honest with its own public, Sefcovic said. Minimal checks can work for goods moving to Northern Ireland from the rest of the United Kingdom, he said, but "zero checks is not an option".

The Commission's proposals to reduce customs documentation and checks would, Sefcovic said, bring stability and legal certainty.

They would also prevent the return of a hard border between Northern Ireland and EU member Ireland, which has been avoided by keeping Northern Ireland in the EU single market for goods.

The fix, agreed as part of Britain's exit from the EU, means goods can flow with ease from there to Ireland, but effectively place a border in the Irish Sea between the British mainland and its province, which has angered some pro-British unionists.

London accuses Brussels of applying the rules on goods trade in a heavy-handed way.

Sefcovic said fleshed-out solutions to the difficulties were "on the table", but needed political will from Britain to move forward.

The commissioner responsible for EU-UK relations also cautioned Britain against slashing EU regulation, which could end EU recognition of British financial services, data and certain food products.

"More divergence means more friction and less trade - simple as that," Sefcovic said.