SDLP leader Colum Eastwood has urged his DUP counterpart not to be "cowing to the leader of the wheelie bin brigade".

The Foyle MP's remarks came after a warning that loyalists will mount street protests if Sir Jeffrey Donaldson leads his party back into Stormont while the Irish Sea border remains in place.

The threat was made in a letter to the leaders of the three main unionist parties from Jamie Bryson on behalf of Unionist Voice Policy Studies, a group that purports to represent a "broad range of groups and individuals across the grassroots unionist and loyalist community".

The letter claims that restoring devolution while the current post-Brexit trade arrangements are in place would "ignite significant instability and, without any doubt, precipitate a return to mass street protests".

Angry @columeastwood can’t engage on the substance: jibes and shouty outbursts is all he has. He has driven the SDLP to their worst electoral position ever. Turns out all the stunts & social media jibes didn’t really even appeal to the nationalist electorate. https://t.co/5opzJY370s

— Jamie Bryson (@JamieBrysonCPNI) October 3, 2023

It says a "significant swathe of grassroots unionism/loyalism" would mount an electoral campaign against any unionist politician who "opted for the role of collaborator and implementer in the subjugation and suspension of the union".

The warning came on the same day as key elements of the Windsor Framework, the revised post-Brexit deal agreed by the EU and UK in February, became fully operational.

Read more: 

• Windsor Framework: All you need to know as the green and red lane system starts
• Jamie Bryson responds to 'rather tiresome' questions on relationship with Stephen Nolan
• Jamie Bryson accuses BBC of 'propaganda for a rebel band' after interview with Belfast rap trio

Mr Eastwood said the DUP's priority should be restoring the devolved institutions.

"The DUP should be listening to people from across our society who desperately need a government to deliver for them – cancer patients waiting months for treatment, SEN (special educational needs) families desperate for urgent support, ordinary people struggling to make ends meet rather than cowing to the leader of the wheelie bin brigade,” he told The Irish News.

Alliance deputy leader Stephen Farry said peaceful protest was "legitimate within a democracy" but that any threats of violence should be addressed.  

"There are many questions regarding the purpose and objectives behind any protesters around the Windsor Framework," the North Down MP said. 

"They don't seem to have any coherent strategy or credible alternative."

On Monday night, Sir Jeffrey responded and said his party is the "main voice of unionism in our sovereign Parliament".

He added: "We believe in devolution and are working to ensure that the local institutions are restored on the basis that they are able to command the support of unionists as well as nationalists on a sustainable long-term basis.

"With the unanimous support of our party officers the Democratic Unionist Party has spelt out its position in relation to the unacceptable nature of the Northern Ireland Protocol and we have taken resolute political action to bring the EU back to the negotiating table. Many said that was unachievable.

"The Windsor Framework represents progress in relation to certain aspects of trade within the United Kingdom and its internal market, but there is more work to do."

He said having already listened to what others have to say, the DUP woud carefully consider any final government response to the issues it raised.

"We will not bow to pressure, threats or blackmail, regardless of what source it comes from," he added.

"Anyone who thinks that they can exert influence on policy or intimidate our party by making such threats is sadly mistaken and misunderstands who we are or where we have come from."