LONDON (Reuters) -Britain's Serious Fraud Office (SFO) has dropped two high-profile corruption probes, into Kazakh miner ENRC and Australian-British miner Rio Tinto, according to updates on its website on Thursday, in the latest blow to the watchdog.
Former FTSE 100 company ENRC was under investigation from 2013 in relation to alleged bribery to secure mining contracts in the Democratic Republic of Congo between 2009 and 2012.
The SFO on Thursday updated a page on its website relating to its ENRC probe, stating that it had closed its investigation as there was "insufficient admissible evidence to prosecute".
An SFO spokesperson declined to comment on the development.
An ENRC spokesperson said: "ENRC is pleased that the SFO has finally closed its investigation and that the SFO is taking no further action in respect of this matter."
The SFO's investigation into ENRC has spawned years of bitter litigation, including lawsuits in London against the SFO, senior officers and ENRC's former lawyers.
Helen Taylor, senior legal researcher at campaign group Spotlight on Corruption, said the SFO "should clarify whether the multiple legal actions the agency and its staff have faced from ENRC played a role in this decision".
The SFO also dropped an investigation into suspected corruption by Rio Tinto in the Republic of Guinea, updating its website on Thursday to say it was "not in the public interest to proceed with a prosecution in the UK".
"The Australian Federal Police maintains a live investigation into this matter and we continue to support their ongoing case," the SFO said.
A Rio Tinto spokesperson noted the announcement, adding: "We are committed to conducting business to the highest standards of integrity."
The decisions come shortly before Nick Ephgrave, the former assistant commissioner at London's police force, replaces current SFO director Lisa Osofsky in September.
The SFO has recently suffered a number of bruising defeats, including the collapse of its case against three former executives at security company G4S and three men's bribery convictions following its Unaoil bribery probe being overturned.
The agency, however, has racked up some significant successes, including mining and trading group Glencore last year being ordered to pay to pay 276.4 million pounds ($349.01 million) for bribery in relation to oil operations in Africa.
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(Reporting by Sam Tobin; Editing by Kylie MacLellan and Jonathan Oatis)