Boris Johnson has been warned that loyalists in Northern Ireland will "not tolerate an economic united Ireland" which is being described as a "betrayal act".

The warning came as a host of loyalists gathered for a meeting at the Constitutional Club in east Belfast.

DUP councillor George Dorrian was among those who attended.

The anger is around claims Boris Johnson has ignored Democratic Unionist Party objections and negotiated a Brexit deal that would create a customs border down the Irish Sea. EU regulations would apply to all goods in Northern Ireland and the DUP would lose its veto on whether the new arrangements come into force.

READ MORE: The four key Northern Irish elements in Boris Johnson's new Brexit deal 

Many unionists inside and outside the party fear for Northern Ireland’s position in the United Kingdom. Even before the deal was unveiled on Thursday, there were cries of betrayal and warnings about tumult and violence. But widespread public disorder seems unlikely.

Jamie Bryson, a prominent blogger and loyalist activist said after the Monday meeting there is "immense anger" within loyalism around the current proposed Brexit deal.

"The unionists and loyalists people aren't being left behind, so if we leave the European Union, we all leave the European Union," he said.   

"Our forefathers went and fought and died for freedom and for the British Parliament to have the sovereignty it has today.   
"Unionists and loyalists are not meekly walking into an economically united Ireland.  It's just not going to happen.  And anyone who thinks it does happen is misguided, is a fool."

Proposals agreed by Boris Johnson and the EU cannot come into force until they are approved by both Westminster and the European Parliament.

A pamphlet advertising Monday night's event described the Prime Minister's deal as the "betrayal act".

The meeting was billed as a 'rallying cry to unionists' which invited the community to voice their views.

It was also described as 'Unionists Unite Against an Economic United Ireland'.

Speaking to media after the meeting concluded, Mr Bryson, one of the speakers at the meeting added "The unionist and loyalist community have had enough of this one-sided peace process, we're not going to tolerate an economic united Ireland and that was the feeling in the room.

"The anger is immense across unionism and loyalism, I can't think of a section of unionism or loyalism who was not represented here tonight in east Belfast so when you ask what was the outcome, no one group was behind this, it's not one group to come up with an outcome, this was the people speaking, this was the unionist and loyalist people speaking.

"They can take that message back to Boris Johnson. For three years Leo Varadkar and the Irish Government went to the European Parliament and everywhere else and said we can't have a border on the island of Ireland because it's a threat to peace, but it's OK we'll just shaft the loyalists and put a border in the Irish sea.

"I think they are entering very dangerous territory at this point in time."

He added: "The message to the DUP is to stand firm, there was DUP representatives in the room tonight, they will have heard the anger from right across the unionist and loyalist community."

When asked whether he was "stoking up violence", Mr Bryson responded: "No one is trying to stoke up violence, but let me say this, it is good enough for the IRA, it's good enough for nationalism including the Irish Government to win concessions and drive us into an economic united Ireland.

"No sensible person wants to see violence, loyalism has spent three years reaffirming a commitment to peace, but ultimately loyalism's support for the peace process and the Belfast Agreement was predicated upon one very simple thing, the union is safe and the threat of violence has been used to undermine the union and drive us into an economic united Ireland and people can read into that whatever way they want."

READ MORE: Boris Johnson confident he can get deal through parliament as DUP 'lose veto' 

The last time Downing Street foisted a deal on Northern Ireland’s unionists in 1985,  the backlash was swift and bitter.

Hundreds of thousands poured on to the streets to protest. A mob punched and kicked the secretary of state outside Belfast city hall. They hit him with a union jack-draped flagpole, grappled him into a headlock and chanted, “Traitor, traitor, traitor.”

That was when Thatcher had signed the Anglo-Irish agreement giving Dublin a say in Northern Ireland’s affairs.

One iconic speech defined the DUP. Their founder, the Rev Ian Paisley, blasted the 1985 Anglo-Irish Agreement with the words: "Never, never, never."