Northern Ireland's First Minister Paul Givan has announced his resignation after a renewed row over post-Brexit trade.

Givan quit on Thursday afternoon as part of a protest by his Democratic Unionist Party (DUP) over trading arrangements.

"It has been the privilege of my lifetime" Given wrote on Twitter, announcing the his resignation in a letter to the speaker of the Northern Ireland Assembly.

He said the Northern Ireland institutions were being "tested once again" and that the "delicate balance" created by several peace agreements has been "impacted" by the UK government and the EU that created the so-called Northern Ireland protocol.

On Wednesday night, the DUP's Edwin Poots, who holds the assembly's agriculture portfolio, said he had ordered a halt on port checks of goods from mainland Great Britain.

The controls are part of the so-called Northern Ireland Protocol to prevent unchecked goods entering the European single market by the back door via neighbouring Ireland.

The DUP claims the protocol, signed separately from the Brexit trade and cooperation agreement between the UK and EU, is harming businesses in Northern Ireland.

It also argues the Irish Sea checks drive a wedge between it and the three other UK nations, threatening Northern Ireland's place as part of the whole country.

Poots' move -- branded a "stunt" by opponents -- came as UK Foreign Secretary Liz Truss was due to hold talks with European Commission vice-president Maros Sefcovic.

Brussels described the move as "unhelpful", saying it "creates further uncertainty and unpredictability for businesses and citizens in Northern Ireland".

A European Commission spokesperson said the agreement was "the one and only solution" to safeguard the 1998 peace deal that ended 30 years of violence over British rule.

As part of that deal, an open land border was mandated between Northern Ireland and EU member Ireland to the south.

Givan's departure, after just eight months in the job, means that deputy first minister Michelle O'Neill, from the pro-Ireland nationalist Sinn Fein party, will also have to quit.

Other ministers in the devolved administration at Stormont could stay in place, but the executive would be unable to make any significant decisions, including on its budget.

Northern Ireland is gearing up for keenly watched assembly elections in May, with the DUP trailing Sinn Fein in opinion polls.

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