Anti-Nice Treaty group The National Platform has called for the resignation of the Minister for Foreign Affairs, claiming Mr Cowen is trying to "overturn" the referendum result.
Mr Cowen has embarked on a course of "high treason" by "conniving" with other EU foreign ministers to "overthrow" the verdict of the Irish people, the National Platform's secretary, Mr Anthony Coughlan, claimed last night.
Mr Coughlan was reacting to the unanimous statement issued by EU foreign ministers after their meeting in Luxembourg yesterday.
In the statement, ministers excluded any reopening of the Nice Treaty and expressed a determination that the ratification process should continue according to the agreed timetable.
Mr Coughlan, however, said this was "a course fraught with danger.
"It is a course that will involve guile, deception, pressure and intimidation - all directed against the Irish people and connived in by its own Government - without any guarantee of succeeding in the end."
He said Mr Cowen could have vetoed the continuance of the Nice ratification process. In view of last week's referendum result, this could not have continued without his consent.
"Did Brian Cowen act independently of the Taoiseach trying to bounce Mr Ahern into a course of folly and disaster for Ireland, for Fianna Fail and for the EU, at the behest of his top Foreign Affairs civil servants?" Mr Coughlan asked.
"It is for the Taoiseach to tell the other EU heads of state and government, meeting in Gothenburg on Thursday, what the verdict of the Irish people is, and to insist that they respect it, not for a conclave of foreign ministers in Luxembourg."
Mr Coughlan claimed that Department of Foreign Affairs officials want Mr Cowen to "do a Denmark" on last week's rejection of the Nice Treaty.
"This means making various political declarations about aspects of the Nice Treaty, but sending exactly the same treaty around for ratification by the Irish people in six months' or a year's time, without changing a jot or tittle of its text.
"Brian Cowen's subscribing to the foreign ministers' statement today is an insult to the Irish people and to the democratic process."
The foreign ministers' statement had all the appearances of an attempt to pre-empt the Government's official position before it had even met, Mr Coughlan concluded.
