Legal claims by financial services workers who have suffered from stress are reaching record levels, law firm GQ Employment Law said on Monday.

Stress-related healthcare problems among bankers were highlighted earlier this month when British bank Lloyds said its chief executive Antonio Horta-Osorio was taking a temporary break after falling ill.

A source familiar with the matter told Reuters that Horta-Osorio's illness was the result of fatigue, and GQ Employment Law partner Jon Gilligan said the recent market turmoil caused by Europe's debt crisis had contributed to a rise in stress problems among financial workers.

The incredibly tough trading conditions and volatility of the last four years has led to record levels of stress and mental illness within the City, said Gilligan.

Gilligan said it was hard to give precise numbers quantifying the extent to which stress-related lawsuits had risen in 2011 from 2010, but he said his firm was taking on more work in this area.

The vast majority of cases tend to get settled out of court, but there are more cases and more higher-value cases coming across our desk this year compared to last year.

Gilligan also cited recent research by the Health & Safety Executive which estimated that 18,000 workers in the UK financial services and insurance sectors had suffered from work related stress, depression or anxiety in the last 12 months.

The struggle to deliver on income targets, the shadow of redundancy and the long hours culture has created a pressure cooker environment, said Gilligan.

If a senior banker or trader is no longer able to work because of stress then that can mean a claim for lost income easily running into the tens of millions of pounds, he added.

(Reporting by Sudip Kar-Gupta; Editing by Jon Loades-Carter)