Britain's membership of the EU "bosses' super-state" will be put to the test at next week's TUC conference after RMT confirmed today that it will table a motion calling for a referendum.
The union is particularly concerned about the recent Monti II proposals, which it says will destroy collective bargaining and employment rights.
Monti II would let courts outlaw strikes on the grounds of "proportionality" and usher in a new era of "social dumping" - where exploited workers are brought to Britain with the sole aim of driving down pay and worsening working conditions.
RMT general secretary Bob Crow said: "We know from our colleagues in Greece, Spain and other parts of Europe that there is a deliberate and co-ordinated effort to grab hold of the austerity agenda to force the pace of privatisation and attacks on working people.
"None of this has happened by accident, it goes right to the very heart of what the EU and its institutions stand for.
"We also know that now that the Euro elite, and their enforcers in the Troika (the ECB, the EU and the IMF), have the bit between their teeth and are upping the ante.
"Their Monti II proposal would give the anti-union Viking and Laval judgements of the European courts full regulatory status, opening the door for attacks on workplace rights and the escalation of social dumping right across the board."
Mr Crow said that if unions dare to fight a judge's ruling on "proportionality" they could be hit with unlimited claims for compensation.
He added: "Monti II isn't some bolt-on extra to the EU machinery, it is consistent with the entire drive of the Euro project and makes a total nonsense of the arguments advanced by those who still try and sell us the con trick of a social Europe.
"It is a fantasy and that is why RMT is once again taking the issue of a referendum on British membership of the EU bosses' super-state to the TUC with a clear call for withdrawal."