The bailout fund set up to help ease the eurozone debt crisis has itself been added to a list of 15 single currency nations at risk of having their credit ratings downgraded.

And there was also a further blow as official figures confirmed that the 17 economies within the euro area grew by just 0.2% in the third quarter - raising fears of recession.

Ratings agency Standard & Poor's (S&P) move to place 15 nations on 'credit watch' could seriously affect six countries with AAA ratings.

They now have a 50% chance of losing their top-rated status, with S&P citing a failure to deliver a convincing solution to the debt crisis.

The only two eurozone members not identified by S&P were Cyprus, which was already under review, and Greece, which holds the world's worst rating.

The agency also decided to place the European Financial Stability Facility (EFSF) on a long term downgrade watch.

Market reaction has been fairly muted on the FTSE 100 (Euronext: VFTSE.NX - news) though the German DAX has dropped over 1%.

On the bond markets, while the German 10-year debt yield rose slightly on opening, countries such as Italy, which had been recently under siege, saw little damage - falling to near 6.4%.

The S&P bombshell came as eurozone leaders tried to prevent the break-up of the single currency and restore stability after weeks of mounting crisis.

Eurogroup chairman Jean-Claude Juncker told German radio that S&P's move was a "wild exaggeration" and unfair.

"I am not unsettled by this, but I am astonished after the significant efforts in recent days to overcome the crisis" he said.

German Chancellor Angela Merkel said the decision was S&P's responsibility. This week's EU Summit would send a signal of confidence and there would be no deviation from her planned path.

After emergency talks in Paris on Monday, Mrs Merkel and French President Nicolas Sarkozy renewed calls for change to the EU Treaty to solve the single currency crisis.

They said they wanted change to be carried out by all 27 member states if possible - or at least the 17 eurozone countries.

The aim would be to allow far tougher rules and sanctions governing the eurozone in future to reassure markets about the euro's long-term stability.

The talks marked the start of a week of intense efforts to settle a eurozone stability deal to convince markets once and for all that the single currency can survive the current economic turmoil.

The key plan is to toughen eurozone checks and balances - something lawyers say will need treaty change.

But it falls short of what many market analysts say is needed to address the debt crisis in the short term.

A credit rating downgrade would make it more expensive for the EFSF to raise money.

Its (Euronext: ALITS.NX - news) borrowing rate stood on Tuesday at 3.75% - hardly a AAA rated figure.

The move towards treaty changes has also prompted fresh difficulties for the UK and Prime Minister David Cameron, as eurosceptic Tories stepped up calls for a referendum on the European Union.

Downing Street insisted that the scale of the proposal - to be put to an EU summit later this week - did not amount to change warranting a referendum in the UK.

But Work and Pensions Secretary Iain Duncan Smith sided with the Eurosceptic right in the Conservatives by suggesting that the impact from any treaty change would demand a national vote.

"The Prime Minister has always been clear, if there are substantial changes that affect Britain's position, then he would go for a referendum because that's what we said to the British public we would do," said Mr Duncan Smith.

Mr Cameron, who will attend a meeting of the European Council in Brussels later this week, insisted nothing had changed to justify such a move.

"Clearly, there are negotiations going on in Europe (Chicago Options: ^REURUSD - news) . I will be part of those negotiations on Thursday and Friday," he said.

"If there is a treaty at the level of 27, and if that passed powers from Britain to Brussels, there would be a referendum.

"We have legislated now so that it is impossible for a British government to pass power from Britain to Brussels without asking the British people in a referendum first."