Troika's days are numbered following ECJ's decision on ECB bond buying: Olli Rehn

Mr Rehn's comments came after an opinion from Europe's highest court in favour of the ECB's controversial bond-buying programme. The opinion means the troika of the ECB, European Commission and International Moneary Fund which has dominated Europe's response to the financial crisis could be broken up, the MEP said.

"This would probably mean the beginning of the end of the troika in its current form, which would in turn push the Eurozone to yet another important institutional reform," Mr Rehn told the 'Financial Times'.

The Euro weakened yesterday after a senior EU legal adviser at the European Court of Justice (ECJ) ruled in favour of the ECB's untested mass bond buying programme which has been dubbed Outright Monetary Transactions (OMT).

The opinion relates to measures drafted at the height of the crisis in 2012. The announcement of OMT is generally regarded as ultimately stabilising the single currency.

Yesterday's interim opinion states that if the OMT programme is implemented, the ECB won't be able to take part in any bailout programme for the country in question.

In his opinion on OMT, advocate general Pedro Cruz Villalon said the ECB must have a broad discretion when framing and implementing the EU's monetary policy.

"And the courts must exercise a degree of caution when reviewing the ECB's activity, since they lack the expertise and experience which the ECB has in this area," the opinion noted.

But the opinion states that in the event of the OMT programme being implemented, "the ECB must, if the programme is to retain its character of a monetary policy measure, refrain from any direct involvement in the financial assistance programme that applies to the state concerned".

The advocate general also cautioned against limiting the ECB's room for manoeuvre, warning against the imposition of a cap on the amount of bonds the ECB could buy.

Setting such a limit "would seriously undermine the effects which the intervention on the secondary markets seeks to achieve, with the risk of triggering speculation", he said.

OMT was unveiled in September 2012 after ECB president Mario Draghi pledged to do whatever it takes to preserve the euro.

The plan calmed financial markets but stirred criticism from Germany's conservative Bundesbank.

The view from the Luxembourg-based court is an important contribution to the current debate on whether the ECB should press ahead with effectively printing money to kick-start the sluggish Eurozone economy.

Had the opinion come out against OMT, it would have raised doubts about whether a possible quantitative easing proposal would pass muster.

The opinion is also a kick in the teeth for opponents of the OMT plan, particularly Germany, which also has strong reservations about quantitative easing.

Experts are waiting for the first meeting of the ECB's Governing Council next week to see if the Frankfurt-based bank will do more to combat deflation and announce a QE programme.

Analysts said that the opinion would be a boost for Mario Draghi.

"We consider the opinion to be a green light for the ECB's OMT and potential QE including government bonds and potential risk sharing in the event of a sovereign default or debt restructuring," said Barclay's economist Thomas Harjes.

The Advocate General said that the ECB must give a proper account of the reasons for adopting an unconventional measure such as the OMT programme, setting out justifications for it.

He added: "The OMT programme decided upon by the ECB... does not infringe the principle of proportionality and may be considered lawful, provided that in the event of the programme being implemented, the obligation to state reasons and the requirements deriving from the principle of proportionality are strictly complied with."

Meanwhile, the World Bank has cut its global growth forecasts for this year and next primarily because of the less than inspiring economic prospects for the Eurozone and Japan. It warned that stagnation in the Eurozone could be protracted by low inflation or even deflation.

"While activity in the United States and the United Kingdom has gathered momentum as labour markets heal and monetary policy remains extremely accommodative, the recovery has been sputtering in the Euro Area and Japan," the Washington-based institution said.

"Global growth is expected to rise moderately, to 3pc in 2015, and average about 3.3pc through to 2017."