A diabetes expert today told a US Congressional committee that he had been pressured by GlaxoSmithKline to back off questioning the safety of its Avandia drug when it came on the market in 1999.

John Buse, a University of North Carolina diabetes doctor said in written testimony today to the The House Oversight and Government Reform Committee that after he raised concern about heart risks with Avandia, company representatives said in phone calls that ``my actions were scurrilous enough to attempt to hold me liable for a loss in market capitalization.''

Buse agreed to work with the company - then known as SmithKline Beecham - on future studies and signed a statement drafted by the drugmaker that was to be used with investors, he said in the written testimony.

His evidence was laid before the committee today which was called after a study released two weeks ago showed that Avandia increased the risk of heart attack by 43 per cent.

Chairman of the comittee Democrat Henry Waxman is concerned about whether the FDA which approved the drug should have been more cautious or warned patients about the dangers.

He told the hearing today: ``Avandia is a case study of the need for reform of our drug safety laws."

Glaxo says the study, published in the New England Journal of Medicine, was based on incomplete evidence and inconclusive methods and that its own studies have yet to find any evidence of extra heart attack risk.

The FDA backed Glaxo up in its own submission saying that there was no clear data showing that the risks were greater.