Beleaguered UK drug-testing firm Huntingdon Life Sciences has lost one of its main backers, in a sign that investors are becoming increasingly wary of being associated with the controversial firm.

Investment bank Stephens Group, Huntingdon's biggest shareholder and one of its leading creditors, said on Wednesday that it plans to sever all ties with the company by the end of January.

All of Stephens' interests in HLS will be taken over by as yet unnamed new investors, the US-based bank said.

The move is a fresh blow to Huntingdon, which has struggled to attract investment since being targeted by campaigners protesting against its use of animals in some drug tests.

Business as usual

HLS chief operating officer Brian Cass on Wednesday stressed that Stephens' withdrawal will not affect the company's financial position or day-to-day activities.

"We look forward with confidence to the continuation of a close and positive relationship with our new bankers and investors as we continue to focus on strengthening our business," he said in a statement.

But the move by Stephens, which owns 15.5% of HLS' shares and has lent the company around �22m, is expected to discourage other major investors from coming forward.

HLS last year moved to switch its main share listing from London to New York in order to attract more US-based investors, who, the company hoped, would be immune from the attacks directed at its UK backers.

A string of UK investors walked away from HLS last year after being targeted by demonstrators.

HLS, which carries out research under contract, has previously claimed that it accounts for only a small fraction of the estimated 2.6 million animals used in drug tests in the UK every year.