THE party that came second in the Northern Ireland Assembly election has been accused of "shameful" behaviour after it blocked the return of the entire legislature.

The Democratic Unionist Party (DUP) said it would not nominate a speaker for Stormont until its demands for overhauling post-Brexit trading arrangements were met.

The DUP’s move means the Assembly is paralysed, unable to hold debates or committees, and unable to consider private member’s bills or question ministers.

There can also also be no election of the First Minister and deputy First Minister, although the DUP had already said it would block that by refusing to nominate a deputy.

DUP leader Sir Jeffrey Donaldson said he was sending a “clear message” to the UK Government and EU to get the Northern Ireland Protocol “sorted”.

Negotiated by Boris Johnson, the protocol effectively puts a trade border down the Irish Sea between Great Britain and Northern Ireland, as the latter is more closely aligned with the EU single market for goods as part of the Brexit deal.

The DUP, who backed Brexit, complain the protocol fundamentally undermines the Union and want it scrapped.

The DUP went backwards in last week’s elections, winning 25 of the Assembly’s 90 seats to Sinn Fein’s 27, the first time the Nationalist party had won a Northern Ireland election.

The new MLAs (Members of the Legislative Assembly) met for the first time in the Stormont chamber today, signing the membership roll before lunch.

However the DUP’s blocking of a new speaker put paid to all other business.

Sinn Fein leader Michelle O'Neill said the DUP’s move was “disgraceful”, while Naomi Long, leader of the cross-community Alliance party, called it “incredibly frustrating”.

Speaking shortly before the plenary session began, Sir Jeffrey said: “We have taken the decision not at this stage to support the election of a speaker.

“I believe that we need to send a very clear message to the European Union and to our Government that we are serious about getting this protocol sorted out.

“Because of the harm it is doing, undermining political stability, damaging the agreements that have formed the basis of political progress made in Northern Ireland, to our economy, contributing to the cost-of-living crisis, this matter needs to be dealt with.

“While others sit on their hands we are not prepared to do that.

“We need decisive action taken by the Government.”

He added: “The choice is clear: if the European Union is serious about protecting the political institutions and the Belfast agreement, and its successor agreements then they know what to do. Equally the same message is there for our own Government as well.

“The ball is firmly at the foot of the Government.”

Ms O’Neill accused the DUP of “disgracefully holding the public to ransom for their Brexit mess”.

She said: “Today is the day we should be forming an executive to put money in people’s pockets and to start to fix our health service. The DUP have confirmed they will punish the public and not turn up. They are disgracefully holding the public to ransom for their Brexit mess. Shameful.”

Ms Long warned Sir Jeffrey not to “overplay his hand” in negotiations with London.

She said: “When you play with fire, you will get burned. We saw this with Brexit where the DUP had influence, they overplayed their hand and they ended up with the mess that we are now in and they’re now asking us all to fix it.

“They are playing with fire again, because the institutions in Northern Ireland cannot survive in the way they are being abused.”

Referring to the possibility of another election if the stalemate continues, she added: “The people who need these institutions most and who need stability in Northern Ireland are unionists, so I would caution Sir Jeffrey about assuming that, in another election, there will be willing partners to go into government beyond it or indeed willing people to fight a further election. We have just had an election.

“It’s incumbent upon us all to accept the outcome of it and to make it work. That’s our job as politicians. I think the DUP is playing a very dangerous game with the institutions and with the future of Northern Ireland.”

Colin McGrath, of the Social Democratic and Labour Party (SDLP), said the DUP leader would try to "cover his tracks for not doing what any democratic society asks people to do".

"The DUP will throw everything they can today to try and defend their indefensible actions," he added.

The Ulster Unionist Party's (UUP) Andy Allen said he understood the DUP's position, but did not agree with the steps they are taking.

"People will come to harm, people will be impacted as a result of that and there needs to be a long hard look at that," he said.

Ireland's Prime Minister said the DUP's action was "unsatisfactory".

Taoiseach Micheal Martin said: “The people elected an Assembly, the Assembly should meet, and then the Assembly should form an executive.

“Yes there are issues that unionism has raised with us in respect of the protocol, but those issues should not prevent the establishment and convening of the Assembly and the formation of the executive.”

Mr Martin said the EU had been “very flexible” over the protocol, and come up with solutions on issues such as medicines being exported from Great Britain to Northern Ireland.

He added: “The evidence is growing that the protocol is having a beneficial impact on the Northern Ireland economy.

“I think there is a need now for pragmatism and commonsense.”