The DUP has held a "forthright meeting" with Irish Prime Minister Bertie Ahern in Dublin.
Mr Paisley raised concerns about the Colombia Three
Party leader Ian Paisley said he warned the Irish government of the implications of allowing NI MPs to speak in the Dublin parliament.
He also raised concerns about the presence of the three Irishmen accused of training guerillas in Colombia.
Earlier the DUP said the NI secretary should resign after saying the economy was "not sustainable in the long term".
The DUP delegation held more than an hour of talks with the taoiseach and Irish Foreign Minister Dermot Ahern.
Speaking afterwards, Mr Paisley said: "If it transpires that Northern Ireland MPs are to be treated on an equal basis with those who are members of the southern (Irish) parliament, then we would consider that a quasi-constitutional claim on Northern Ireland.
"Such an unfriendly act of aggression against Northern Ireland's sovereignty would not be tolerated by us as unionists."
He added: "In addition to the North-South aspect of our meeting we have again restated our view that as far as the DUP is concerned there can be no fudging of the line between democracy and terror.
"We agree with the sentiments of the taoiseach and the Irish Minister for Justice that the IRA must be gone and out of business for good."
Dermot Ahern said he would hold further talks with NI parties at Hillsborough Castle before Christmas.
"We are under no illusion that while we don't want a vacuum to be created, at the same time we will try and tic-tac with the parties between now and January," he said.
"Then, depending what happens in January, the IMC report will be issued and that will be key.
The DUP has called on Peter Hain to resign
"Depending on what they say, we would expect progress to happen thereafter.
"If it is the case that the IMC, in some way are not able to give in effect a clear indication that there is an end to paramilitary activity and criminality then we obviously have to wait and see what happens thereafter."
Speaking about the Dublin meeting, Sinn Fein's Martin McGuinness said "the DUP need to come to terms with the current political realities and engage with" his party.
"The unionist community needs confident and positive leadership. They need politicians who can deliver for them," he said.
"There is no way to do this other than through the institutions of the Good Friday Agreement, which means entering into government with Sinn Fein."