A legal challenge against the Democratic Unionist Party's (DUP) boycott of most cross-border ministerial meetings resumed on Friday.

Earlier, another virtual ministerial meeting was cancelled.

Stormont minister Nichola Mallon and the Republic of Ireland's environment minister logged on, but her DUP colleague Edwin Poots failed to show.

On Monday, the High Court ruled the DUP's boycott of such talks was "unlawful".

The man behind the challenge, Sean Napier, said he had instructed his solicitors to request a hearing for Friday afternoon about the DUP's non-attendance.

He said the rule of law and the protection of the Good Friday Agreement "must prevail".

The DUP boycott of most North-South Ministerial Council (NSMC) meetings was announced by party leader Sir Jeffrey Donaldson last month.

The NSMC is the main body for cross-border co-operation between the governments of Northern Ireland and the Republic of Ireland.

It is attended by ministers from both sides of the border who oversee joint working in areas such as trade, food safety and agriculture.

The DUP is refusing to attend in protest against the Northern Ireland Protocol.

The protocol is part of the Brexit deal agreed in 2019 and was introduced to help prevent checks along the border between Northern Ireland and the Republic of Ireland.

But unionists say it creates a barrier to trade between Great Britain and Northern Ireland, and undermines the latter's position in the UK.

The NI minister Ms Mallon said the boycott must end.

She had been due to discuss cross-border aquaculture with her counterparts.

"It is astounding following this week's High Court ruling that Jeffrey Donaldson is overseeing a deliberate and unlawful boycott of the north-south institutions," she said.

"It shows only disdain for the rule of law but utter contempt for the people we represent."

On Thursday, ministers attended a NSMC meeting on health issues.

The DUP said this was in line with its position.

When asked on Thursday whether the DUP would continue its boycott, Sir Jeffrey told BBC Radio Foyle "our position remains as it has been".

Sinn Féin junior minister Declan Kearney said that "this inaction by Minister Edwin Poots and the executive office is a serious failure to comply with the law and the ministerial code which require ministers to participate in meetings of the NSMC".

He added: "These institutions are about joining up services across the island and delivering on important issues which impact on people's lives such as health, education and millions of pounds in funding. 

"It's time the DUP put ordinary people's interests first by ending this illegal boycott of vital government business and get back to work on behalf of everyone in our society."