A crackdown on misdemeanors in the finance industry has helped to reduce the leaking of M&A deals before they are made public to the lowest level since the financial crisis, according to a survey, which also found Hong Kong was the leakiest market.

Last year, just six percent of deals leaked, against an average of 7.4 percent in 2009-2014, the survey found. It was commissioned by Intralinks Holdings, which provides services for managing M&A deals, and conducted by Britain's Cass Business School.

It said the overall fall in leaks was due to tighter regulation and internal governance, as well as the increased risks that a leak presents to a transaction.

The survey measured significant price rises in the shares of a target company in the weeks before a deal officially emerged. It found that the leakiest market was Hong Kong, where an average 18.6 percent of all deals involving Hong Kong-listed targets seeped out prematurely. That was followed by India with 15.2 percent and Britain at 14.1 percent.

"There has been a dramatic rise in regulatory enforcement and actions in the past 18-24 months, not least in the fines that have been imposed," Professor Scott Moeller, Director of the M&A Research Centre at Cass Business School, said. He was referring to penalties incurred on offences such as the rigging on interest rate benchmarks like Libor.

"You begin to get an environment where people are saying, wait a moment, is this (leaking) in fact worth it."

Leaks in the United States, the world's hottest M&A market, average about 6.6 percent of deals, while Australian dealmakers are the tightest-lipped with just 3.5 percent of transactions leaked.

But the survey also showed that the takeover premium paid by acquirers was significantly higher when a deal was leaked. The median takeover premium for leaked deals was 51.2 percent in 2009-2014, versus 29.2 percent for those kept under wraps, although the former took longer to complete than the latter.

That could be because leak deals are more likely to attract rival bidders, Moeller said.

Global M&A activity has soared to record highs this year, rising 41 percent on 2014 to $3.8 trillion in the year to date, according to Thomson Reuters data.