The UK has asked for more time to respond to the legal action taken by the European Union over its unilateral decision to ease the requirements of the Northern Ireland Protocol, RTÉ News understands.

The request came in two letters from the UK's chief Brexit minister David Frost.

The EU launched twin-track legal proceedings against the UK on 15 March following the decision by the Northern Ireland Secretary Brandon Lewis to unilaterally delay the full implementation of the protocol.

The commission had issued a "letter of formal notice" to the UK government, which is the first step in a legal procedure which could end up in the European Court of Justice.

The letter of formal notice accused the UK of "breaching the substantive provisions of the Protocol on Ireland and Northern Ireland" as well as the "good faith obligation" enshrined within the Brexit Withdrawal Agreement.

A second "political" letter was sent by the European Commission Vice President Maroš Šefcovic to Mr Frost calling on London "to rectify and refrain from putting into practice" the announced extension of the grace period for certain border checks on goods moving across the Irish Sea from Great Britain to Northern Ireland.

The UK was given one month to respond to the two letters.

However, two sources have told RTÉ News that Mr Frost has asked for an extra month to respond to the legal action.

One source described the two letters as "courteous" and "respectful".

It is understood Mr Frost stressed in the letters that the UK was convinced that its unilateral actions in extending grace periods and cancelling other requirements of the protocol were a bona fide attempt by the UK to comply with its obligations.

He is also understood to have stressed the complexity of the issues involved.

When it unilaterally extended grace periods on 3 March, the British government argued that the move amounted to a short term, practical step that was required to avoid any food shortages from 1 April, when the mutually agreed grace period related to EU food safety requirements expired.

A UK government spokesperson said: "In line with precedent that typically allows two months to respond to proceedings of this kind, we have agreed with the EU that we will respond to the Letter of Formal Notice by mid-May.

"We've been clear that the measures we have taken are lawful and part of a progressive and good faith implementation of the Northern Ireland Protocol."

The Minister for Foreign Affairs Simon Coveney, is in London today and tomorrow for a number of meetings in relation to Irish and EU-UK relations, the implementation of the Northern Ireland Protocol and the recent violence in Northern Ireland.

He'll meet with British Foreign Secretary Dominic Raab, Secretary of State for Northern Ireland Brandon Lewis and Minister of State at the Cabinet Office David Frost.

He is also due to meet with Leader of the Opposition Keir Starmer, Shadow Secretary of State for Northern Ireland Louise Haigh and Shadow Foreign Secretary Lisa Nandy.