LONDON Tue Mar 3, 2015 6:15am EST

Chances of Greece leaving the euro zone in the next 12 months are the highest since late 2012 even though Athens's financial lifeline has been extended, a survey of investors based mainly in Germany showed on Tuesday.

The survey of 980 individuals and institutional investors registered with consultancy firm sentix, found that 37.1 percent of respondents expect Athens to leave the currency bloc, up from 22.5 percent in January.

These expectations have risen steadily from a record low 5.7 percent hit last July, but remain below highs of 70.7 percent seen at the height of the euro zone debt crisis in July 2012.

A Reuters poll of economists in mid-February gave a one-in-four chance of Greece leaving the currency area in 2015.

"The new aid program for the country does not seem to be convincing, rather a "Grexit" is now bound to be a constant topic among investors for the months to come," said Sebastian Wanke, a senior analyst at sentix.

The poll was conducted between Feb. 26 and 28.

Greece secured a four-month extension to its bailout on Feb. 24, after tense negotiations between Athens and its euro zone partners but still faces acute funding problems and could run out of cash by the end of March.

Spain's economy minister said on Monday that euro zone countries were discussing a third bailout for Greece, worth 30 billion to 50 billion euros, but EU officials said there were no such talks.

The sentix survey -- in which respondents may choose up to three countries they think will quit the currency union in the next 12 months -- put the chance of any country leaving the bloc at 38 percent.

The Euro Break-up Index (EBI) last reached this level in March 2013 after inconclusive elections in Italy and a banking crisis in Cyprus which saw the country become the fourth euro zone member to be bailed out.

The EBI hit a high of 73 percent in July 2012, and touched its low at 7.6 percent in July 2014.

Peter Schaffrik, head of European rates strategy at RBC, said the bailout extension alone had not removed fears Greece will leave the 19-member euro zone.

"So far there is an agreement in principle, but have they really made substantial progress? I'm not so sure," he added.

"What we need is implementation, and for both sides to live up to expectations, and then we can become a bit more relaxed."