Questions raised about independence of International Institute of Strategic Studies after multimillion-dollar deal.

The UK Charity Commission has confirmed it is investigating a complaint filed against a London-based think-tank into whether it compromised its independence by accepting confidential financing from the Gulf state of Bahrain.

Documents leaked by rights watchdog Bahrain Watch indicate Bahrain’s government started funding the International Institute of Strategic Studies (IISS) in October 2010 to the amount of roughly $7.6m a year, after a secret agreement was signed.

That amount covers both the Manama Dialogue, a three-day conference that begins on Friday, as well as IISS offices in Bahrain’s capital.

The revelations have been controversial, with suggestions that funding from the Gulf kingdom, frequently accused of rights violations and media crackdowns, might hamper the independence of the British think-tank.

“There is not a legal requirement to disclose the identity of donors,” a Charity Commission spokesperson told Al Jazeera over the phone.

The commission – which regulates the operation of charities in the UK, as IISS is registered – received the complaint on Wednesday.

“Trustees, however, must recognise the importance of maintaining the independence of their charity, whether from funders, stakeholders or government. Trustees’ decisions must be made independently and in the interests of the charity.”

Fahad Desmukh, a researcher with Bahrain Watch, acknowledged that Bahrain’s funding of IISS is largely in line with what other governments have done – including Egypt, Israel, Qatar and Kenya.

The amount of money, calculated to be roughly a third of IISS’s funds, is what concerns him.

“We don’t know the full extent [of Bahrain’s funding] – these are just the projects that we know of – it could be higher,” said Desmukh.

READ MORE: Bahrain authorities block Al Jazeera from GCC summit

Al Jazeera asked both IISS and Bahrain’s Ministry of Foreign Affairs why the memorandum of understanding between the two had to be kept secret.

Calls and emails to Bahrain’s Ministry of Foreign Affairs were not returned.

James Clements, media and communications manager at IISS, told Al Jazeera he was “not doing any interviews or answering any questions” on the subject.

He forwarded a statement from IISS that “rejects” any allegations that its independence is compromised by Bahrain’s funding. It also said the think-tank “does not participate in any manner of advocacy”.

IISS said on its website: “In all dealings with potential funders, we insist clearly and consistently that we will not accept any funding that may impinge on our intellectual and political independence. This is never a matter for negotiation.”