The Rev Ian Paisley has said he will fight plans to expand the North-South bodies set up under the Belfast Agreement.
Dr Paisley was reacting after the North's First Minister said on Monday he supported further all-Ireland co-operation in certain key areas.
Mr David Trimble was speaking at Stormont following a meeting of the North-South Ministerial Council (NSMC) jointly chaired by him and the Deputy First Minister, Mr Mark Durkan.
The meeting was also attended by the Minister for Foreign Affairs, Mr Cowen.
Mr Trimble said: "Since the agreement the operation of the NSMC structures has not given rise to any controversy at all.
"It shows that in the agreement we got the architecture right, and people can see the procedures.
"There is transparency and accountability. It is therefore quite natural to think in terms of the possibility of formalising within the NSMC other areas of co-operation."
But Dr Paisley countered this yesterday, warning: "We do not intend to allow Trimble to hoodwink voters so that he can pursue his own concession-granting agenda."
He said: "It is no surprise that the Dublin Government wishes to increase the number of implementation bodies but I am startled at the speed to which David Trimble has agreed to expand those bodies.
"Once again Trimble is embarking on a plan to short-change unionists, thus allowing Dublin to interfere in matters that affect the people of Northern Ireland on a daily basis."
The DUP leader complained that the bodies were unaccountable to both the Assembly and the voters of the North.
He further claimed that he was constantly refused permission in the Assembly to raise questions regarding them.
At Monday's meeting Mr Cowen, along with Mr Trimble and Mr Durkan, noted progress regarding the six implementation bodies and Tourism Ireland.
They recommended a budget of some £54 million sterling for the next financial year.
They also agreed to undertake further work relating to all-Ireland co-operation within a European context.
Following the meeting, Mr Cowen travelled to Armagh city to visit the Centre for Cross-Border Studies, which is part of Queen's University Belfast.
Praising what he called "partnership politics", Mr Cowen said: "Only those who live in absolute denial of geographical reality or the logic of economy of scale could deny the simple common sense of approaching certain issues on a cross-Border or all-island basis."
He said he experienced a sense of history and "quiet satisfaction" that he could, as a southern Minister, attend an NSMC meeting at Stormont without excessive hype or drama.