Britain's chief Brexit negotiator David Frost arrives for a meeting with European Commission's head of Task Force for Relations with Britain in Brussels on Nov 16, 2020. (KENZO TRIBOUILLARD / AFP)

David Frost, Britain’s top Europe adviser and chief Brexit negotiator, has called on the European Union to “shake off any remaining ill will” toward Britain for leaving the bloc.

In an opinion piece for The Sunday Telegraph, Frost said that Brussels must focus on making Brexit a success and defended recent unilateral alterations to trade arrangements concerning Northern Ireland, which continues to be a bone of contention.

News agencies reported the European Commission intends to take legal action after the UK last week announced it was extending “grace periods” on post-Brexit customs checks designed to ease trade between Northern Ireland, which remains in the EU single market for goods, and the rest of Britain.

The EU claims this is a breach of the terms of the Brexit deal agreed last year. Frost said last week the grace periods would allow time for “constructive discussions” with Brussels.

News agencies reported the European Commission intends to take legal action after the UK last week announced it was extending “grace periods” on post-Brexit customs checks designed to ease trade between Northern Ireland, which remains in the EU single market for goods, and the rest of Britain

The Northern Ireland protocol in the Brexit Withdrawal Agreement was designed by the EU and UK to avoid a hardening of the border on the island of Ireland.

“I hope they will shake off any remaining ill will towards us for leaving, and instead build a friendly relationship, between sovereign equals,” Frost wrote.

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“That is what I will be working towards, acting constructively when we can, standing up for our interests when we must — as a sovereign country in full control of our own destiny.”

The EU threatened a hard border on the island of Ireland in January as it sought to control COVID-19 vaccine exports. But it was forced to backpedal followingheavy criticism from both Ireland and the UK.

In his piece for the Telegraph, Frost said the EU’s behavior“has significantly undermined cross-community confidence in the protocol” and that the UK move to smooth trade was lawful and designed to protect the everyday lives of people in Northern Ireland.

Frost also said the UK’s independent vaccine rollout, in contrast to the EU’s supply program, was an example of the benefits of Brexit.

He said: “I have always believed that the gains of controlling our own affairs outweigh the short-term adjustments. That is what Britain has chosen.”

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He went on to say he believed Brexit would allow the UK to play a more influential role on theworld stage.