By Ben Hirschler

LONDON, March 18 (Reuters) - The gap between regulatory decisions on new medicines made in different parts of the world is increasing, imposing a high cost on industry and deterring investment, the head of research at France's Sanofi said on Wednesday.

Elias Zerhouni, speaking at a conference in London to mark the 20th anniversary of the European Medicines Agency (EMA), said there was an "urgent" need to harmonise regulations, potentially through discussions at the G8 or G20 groups of nations.

Previously an academic researcher and director of the U.S. National Institutes of Health before moving across to industry, Zerhouni said the divergent regulatory systems were at odds with the global nature of research and the drug supply chain.

"In my short experience of five years, I have not seen a single regulatory decision that was fully consistent across regulatory agencies," he said.

While the EMA has harmonised the approval of new drugs in Europe since its formation in 1995, there is very often a gulf in opinions about the risks and benefits of a particular medicine between regulators in Europe, North America and Asia.

"There are increasing regulatory differences across the regions," Zerhouni said. "It imposes an enormous cost on the innovator. I spend 20 percent of our R&D budget trying to mix and match in order to do the convergence between different systems."

An analysis of drug approvals in recent years showed views diverged between the EMA and the U.S. Food and Drug Administration (FDA) on whether to allow or deny approval of new drugs in 22 percent of cases, he said.

There were also significant differences on drug labels -- the official descriptions accompanying a drug that spell out the claims that can be made about it -- in 50 percent of cases.

Zerhouni cited as an example the EMA allowing Sanofi to make more claims about the benefits of its new insulin drug Toujeo than the FDA.

He said there are also big variations in the timing of decisions about the steps along the way in assessing new drugs, leading to frequent delays in conducting clinical trials.

(Reporting by Ben Hirschler; Editing by Ruth Pitchford)