Tens of billions of euro that banks in the eurozone have set aside for loan losses may have substantially reduced their chances of failing ECB stress tests.

A total of €71.5bn was set aside in 2013 by the 20 biggest listed banks involved in the exercise, a Reuters analysis of their new annual reports shows. Many also boosted capital ratios by raising cash and hoarding profits.

If replicated across all 128 lenders subject to tests that the European Central Bank aims to complete by October, it could mean no bank will fail or be forced to raise large amounts of new capital. Such limited consequences helped discredit previous tests by EU financial watchdog the European Banking Authority (EBA) – one reason the ECB is keen to show that its new exercise will truly be tough on the region’s banks.

While some analysts have suggested that a failure by the ECB to force the closure of any eurozone bank after its own tests could again undermine the credibility of the exercise, many see it as more important that the ECB’s scrutiny creates a stronger banking system – something the data suggest is happening.

“A lot of action has been taken,” said Carla Antunes da Silva, head of European banks’ research at Credit Suisse. “I don’t think you need to have a day of reckoning where a big bank needs to fail.

“A few years ago, if you had asked investors what they wanted to see from stress tests they would have said ‘bodies’ – but not any more,” she added.

A survey last month of 200 clients of her own bank had, she said, found very few seeing it as essential to the credibility of the ECB stress tests that a major bank should fail.

ECB President Mario Draghi himself has highlighted progress already made since they learned of his plans and said this month he was “pretty confident” that the testing regime would “find a stronger banking system than we had before announcing it”.

The EBA, which will co-ordinate this year’s stress tests with the ECB, said investors were interested not just in whether banks pass or fail but their sensitivity to stress and how supervisors deal with the results.

“The credibility of the EU-wide stress test rests on transparency; market participants will determine for themselves how supervisors and banks are dealing with remaining pockets of vulnerability.”

Back in January, analysts at Keefe, Bruyette & Woods published a report showing 27 of the ECB’s 128 banks failing a simulated stress test, though of these only Commerzbank was among the top 20 listed entities. The German lender has said it is “well prepared” for the exercise.

One senior official at a banking regulatory body in Europe told Reuters that he and his peers would not be concerned if the ECB review failed to force significant remedial action at major banks. However, several experts, speaking privately, emphasised that it could throw up surprises and problems.

But large provisions already taken by banks do not mean they are out of the woods.

Karl Whelan of University College Dublin, who advises the European parliament’s economics committee, said: “There’s no doubt that banks have been building up their capital ratios.

“But these ratios often hide a lot,” he warned.