The Alliance Party leader has proposed a recall of the Stormont Assembly, following days of violence and disorder in parts of Northern Ireland.
Naomi Long has called for MLAs to debate a motion condemning the recent violence and attacks on police in loyalist areas.
The party will need the signatures of 30 MLAs for the Assembly to be recalled this week.
SDLP deputy leader Nichola Mallon confirmed on Tuesday that the party will sign the motion.
The move comes after police were attacked during another night of violence in a number of loyalist areas on Monday.
Nine officers were injured in Ballymena, taking to 41 the number injured in disorder across Northern Ireland since Friday night.
The most intense clashes on Monday were witnessed in Ballymena, when nine riot police officers were injured after they intervened in unlawful march of loyalists through the town.
During the unrest, debris, including a wheelie bin, was thrown onto the M2 motorway, forcing its closure.
Disorder also flared in parts of Carrickfergus, Newtownabbey and Londonderry on Monday, with petrol bombs and other missiles thrown at officers.
The violence comes amid soaring tensions within the loyalist community over post-Brexit trading arrangements, which have created new regulatory and customs barriers between Northern Ireland and the rest of the UK.
Anger ramped up further last week following a decision not to prosecute 24 Sinn Fein politicians for attending a large-scale republican funeral during Covid-19 restrictions.
All the main unionist parties have demanded the resignation of PSNI Chief Constable Simon Byrne, claiming he has lost the confidence of their community.
However, non-unionist parties in Northern Ireland have accused unionist leaders of creating the febrile atmosphere and stoking up tensions.
Commenting on the latest night of violence, Police Service of Northern Ireland Chief Superintendent Davy Beck branded the violence “disgraceful”.
“The disorder we witnessed last night, and which our officers had to deal with, is extremely disappointing,” he said.
“Yet again we have seen people make a deliberate decision to damage our communities and target our officers.
“Not only did their reckless and criminal behaviour place the lives of our officers in danger, but such senseless behaviour shows the blatant disregard those responsible have for the safety of others by throwing debris onto a motorway.
“It is extremely fortunate no one was seriously injured, or worse.”
In a statement on the Assembly recall, Ms Long said: “The violence has to stop, but so does the political cover given through vague comments and empty threats.
“There is no room for ambiguity, this violence must be condemned by a united Assembly, which fully supports the rule of law in Northern Ireland.
“Anything less is just allowing a culture of lawlessness to grow and further poison our community.”
Children as young as 12 have been involved in some of the violence that has been witnessed in recent days.
Cars, a JCB digger, a phone box and bins were set alight in the Waterside area of Londonderry on Monday.
Police said that a brick was thrown at a taxi, which was carrying a passenger at the time, on the Limavady Road.
Officers from the PSNI Tactical Support Group (TSG) attended the loyalist Nelson Drive Estate, where a group of youths clashed with police.
The surrounding roads were blocked with fires and barricades.
It marked the seventh night police came under attack in Derry.
There was also some disorder earlier in the evening in a nationalist area of the city near Templemore Road when youths threw stones at officers attending a security alert in the area.
Petrol bombs were thrown at police officers in a loyalist area of Carrickfergus and a crowd of young people gathered in the North Road area and lit a fire in the middle of the street.
An 18-year-old man was arrested in the Co Antrim town on suspicion of possessing articles for use with petrol bombs.
He remained in custody on Tuesday afternoon.
As well as the loyalist march in Ballymena on Monday, there were similar scenes in Portadown and Markethill as loyalists, many of them masked, took to the streets.
The processions were not notified to the Parades Commission as required for such events in Northern Ireland.
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