LONDON (Reuters) - A regulatory crackdown has failed to prevent merger and acquisition (M&A) deals being leaked before their official announcement, a survey showed on Thursday, suggesting potential benefits of unauthorised disclosures outweigh the risks.

Globally deal leaks increased to 8.6 percent of all deals in 2015, compared to 6 percent in 2014, research from Britain's Cass Business School and Intralinks, which sells deals management tools, said.

"One interpretation of these findings suggests that even an increased threat of enforcement is still not enough to deter leaks: in short, for some the potential benefits of leaking a deal still appear to outweigh the risks," said Philip Whitchelo, a vice president at Intralinks.

The study found that in 2015 targets in leaked deals achieved significantly higher takeover premiums than those in non-leaked deals which was in line with the long term trend.

The median takeover premium for targets in leaked deals was 53 percent compared to 24 percent for non-leaked deals, the biggest gap between the two for four years.

With one in five deals, India saw the highest proportion of leaks, followed by Hong Kong and the United States where 12.9 and a seven-year high of 12.6 percent of deals respectively were leaked in 2015.

The top three sectors for deal leaks in 2015 were Real Estate (12.9 percent), Healthcare (12.5 percent) and Energy & Power (9.3 percent).

The report said the number of enforcement actions by major U.S. regulators, which include deal leaks, rose in 2015 compared to 2014. The financial penalties levied by the US Securities and Exchange Commission and the Hong Kong Securities and Futures Commission also increased compared to 2014.

However the number of enforcement actions by Britain's Financial Conduct Authority in 2015 was the same as in 2014 and the total sum of financial penalties levied fell by 38 percent in 2015 compared to 2014, the report said without citing a reason.

The report was based on an analysis of 5,024 deals announced between 2009 and 2015, of which 378 were identified as leaked deals.

(Reporting by Dasha Afanasieva; Editing by Alexandra Hudson)