Huntingdon Life Sciences, the beleaguered animal research group, has confirmed that its mystery backer is Stephens Group of the US.

The Little Rock, Arkansas-based investment firm stepped in earlier this month to save Huntingdon from receivership over a �22.6m loan owed to Royal Bank of Scotland and two US banks.

Animal rights activists had vowed to identify and target the investor as part of their campaign to see Huntingdon closed.

Stephens Group is Huntingdon's largest shareholder, with a 15.7% stake.

It is believed to have given Huntingdon a loan repayable by 2006 and be discussing providing working capital.

UK government officials were reported to have been involved in the negotiations.

'Stephens will suffer'

Greg Avery of protest group Stop Huntingdon Animal Cruelty was quoted in the Financial Times as saying: "It's time now to try to damage Stephens in many different ways.

"Stephens will very soon be suffering for helping HLS."

Huntingdon shares edged up half a penny to 9.5p in early trading on Monday, up from a 2001 low of 1.75p but well below last year's high of 27.75p.