Brendan Barber of the British Trade Union Congress (TUC), Annelie Butenbach of the German Trade Union Confederation (DGB) and Bernard Thibault of the French General Confederation of Labour (CGT) were among those attending an unplanned 'extraordinary' steering committee meeting of the European Trade Union Confederation (ETUC) summoned in response to the treaty.
A declaration they adopted says the proposed treaty calls for austerity and budgetary discipline "at a time when most economies are still weak and unemployment intolerably high."
ETUC Secretary-General Bernadette Ségol said: "European trade unions are mobilising to say that 'enough is enough', austerity measures are not the only answer to the crisis. On the contrary, they produce enormous social damage."
The most recent official EU statistics indicated that eurozone unemployment had stabilised in November 2011 at 10.3%, the highest in the currency union's history. People under 25 are on average twice as likely to be unemployed and some countries, notably Spain and Greece, are much more affected than others.
Judith Kirton-Darling of ETUC said: "The IMF, the OECD, the ILO, even Standard & Poor's, which are hardly the friends of the trade union movement, are all saying 'this is the wrong thing to be doing, this is the wrong medicine, and it can only make the situation worse'."
Federalist and Keynesian prescriptions
The declaration makes a number of prescriptions including changing the European Central Bank's (ECB) mandate to give it an obligation to act as a 'lender of last resort'.
ETUC argues that a new ECB mandate would allow national governments to borrow at low interest rates on the financial markets and so "put a stop to irrational but self fulfilling financial sector herd behaviour."
Trade unionists also pushed to maintain "investments for growth". These could be financed through eurobonds or a tax on financial transactions. Earlier this month a French minister asserted such a tax would be implemented this year, though EU governments remain sharply divided on the matter, with strong opposition from the United Kingdom.
Spain and Italy recently had unexpectedly successful sales of government debt. However, the interest rates they pay for long-term debt remain perilously close to levels considered by many economists to be unsustainable (5.4% and 6.2% respectively on 10-year bonds).
Coordinated action on eve of March summit
Union leaders pledged to take common action on 29 February to protest the fiscal compact treaty, on the eve of a 1 March EU leadership summit where it is expected to be signed.
"There will be actions in all countries with the same line and the same logos in all of Europe," said Jean-Michel Joubier, Europe-international officer with the French CGT.
However, the unions have not yet decided what action they will take in each country. "The idea is to have protests. In some countries it will be symbolic but it can go up to strikes," Joubier said.
The action would depend on the different traditions and legal situations of each country. It is unclear how significant the protests will be.
Belgian trade unions are independently planning a general strike on 30 January, timed to coincide with a European Council summit. A strike in Belgium on 22 December paralysed all rail transport and some airports in the country.
Though unions are for the most part protesting austerity measures implemented by national governments, the belt-tightening has largely been at the urging of the European Commission.