A former Allen & Overy associate has claimed that Goldman Sachs exploited its relationship with the Libyan Investment Authority (LIA) to sell more than a billion dollars' worth of complex derivatives to the sovereign wealth fund, promoting risky investments which ended up making a significant loss.

The LIA has made a $1.2bn (£750m) High Court claim relating to nine large long-dated complex financial derivative transactions which the fund entered into with Goldman between January 2008 and April 2008.

In a witness statement to the High Court, Catherine McDougal, who worked in A&O's project finance team in London between 2006 and 2008 and was seconded to the LIA around the time of the disputed trades, claims that the LIA equity team's knowledge of financial products was "extremely limited" and they had conducted no due diligence whatsoever around the trades.

The LIA instead relied on Goldman banker Youssef Kabbaj, who, according to McDougall, abused his position as a close and trusted friend of the fund.

"I was shocked by what I learnt whilst on my secondment with the LIA," her statement to the court reads. "It was readily apparent to me that Goldman had unfairly taken advantage of the LIA's lack of financial sophisticion and the trust and confidence that the various members of the LIA had reposed in them, and had sold the LIA $1 billion worth of derivative products that the LIA did not properly understand." 

As evidence, she cites a separate project finance deal where the fund retained Freshfields Bruckhaus Deringer, yet the LIA's legal head Albudery Shariha had no knowledge of what was in the retainer letter and was unaware that there had been no up-front negotiation of fees.

McDougall's secondment to the LIA, which was originally due to last three months, was cut short at six weeks, she says, after A&O received a "serious complaint" from the client and pulled her from the country.

Australian-qualified McDougall says that the firm was preparing disciplinary action against her, but she left without undergoing any formal process.

McDougall adds that a number of A&O partners had approached her to express their concern about the relationship between Goldman and the LIA. However, her witness statement also recalls that colleagues in London "were very interested in all of this as they thought the LIA did not know what they were doing and they thought it was an excellent client-business opportunity for them."

Litigation boutique Enyo Law, led by partner Simon Twigden and supported by partner Edward Allen, is acting on behalf of the LIA. Allen is also reported to have met with officials from the U.S. Securities and Exchange Commission in connection with a separate investigation into Goldman being run by the regulator.

It is understood that Herbert Smith Freehills, led by its banking litigation head Damien Byrne Hill, is acting for Goldman Sachs.

A&O declined to comment.