In a highly anticipated London High Court trial, Eurasian Natural Resources Company (ENRC) alleges that law firm Dechert and its former partner, Neil Gerrard - hired to carry out an internal investigation into a whistleblowing report - disclosed privileged and confidential information to the SFO.

Former SFO director Richard Alderman was "desperate" to nail a high-profile corporate suspect in 2011 and Gerrard wanted to milk ENRC for vast fees by expanding the scope of his internal investigation, that at times employed more than 50 Dechert fee earners, ENRC alleges in documents filed with the court.

Dechert and Gerrard dismiss the allegations as "an elaborate work of fiction". The SFO, which has faced particularly stinging criticism over the collapse of a prosecution last month, rejects all claims against former senior staff as "hopeless", according to court filings.

Both sides will lay out their defence in court later this week.

The SFO opened a criminal investigation into ENRC in 2013 over allegations of fraud, bribery and corruption surrounding the acquisition of mineral assets in Africa - five months before ENRC crashed out of London's blue-chip index.

No charges have been brought against the company or current or former officers.

Alderman, who stepped down from the SFO in 2012, former interim director Mark Thompson and David Green, who held the reins for six years, are among those who have been called to testify in the 11-week trial - one of a string of lawsuits filed by ENRC since the eight-year investigation began.

Co-founded by three billionaire Kazakh businessmen and the Kazakh government, ENRC alleges Gerrard used close SFO contacts as "personal confidants" when disclosing information, breaching his contract and fiduciary duty to ENRC, and leaked privileged material to newspapers.

ENRC, which alleges the SFO incited and encouraged Gerrard's conduct, accuses the investigator and prosecutor of misfeasance in public office and is seeking public vindication and damages for "very significant losses".

($1 = 0.7048 pounds)

(Reporting by Kirstin Ridley; Editing by Kirsten Donovan)

By Kirstin Ridley