One of the world’s leading law firms has been forced to address allegations that it advised on a deal for the son of Equatorial Guinea’s dictator to purchase a $38m private jet.

Clifford Chance said it had not acted for Teodorín Obiang in the deal to acquire the jet in 2006, but that it had advised a third party on the sale. It also said it advised Obiang personally when US law enforcement accused him of corruption and attempted to seize his assets in 2011. It said it would not accept him as a client today.

There is no suggestion of criminal wrongdoing by Clifford Chance. However, the firm’s statement comes amid increasing focus on the role of “professional enablers”, such as lawyers, bankers and accountants, who wittingly or unwittingly provide services to corrupt figures.

Last year Obiang was convicted of corruption and embezzlement by a French court, which gave him a three-year suspended sentence and seized assets worth €107m, including a mansion near the Champs-Élysées. Obiang has appealed to the United Nations, claiming that he has diplomatic immunity from prosecution.

Clifford Chance, which reported revenues of £1.6bn and profits of £626m last year, issued its statement after Private Eye published the allegations last month.

In the statement, Clifford Chance’s general counsel, Chris Perrin, said the firm had acted for an entity that lent funds to the seller of the jet, rather than for Obiang as purchaser. It acknowledged acting for him when the US attempted to seize his wealth, but said it would not do so now.

“At the time, we saw that as an access-to-justice issue, and we therefore agreed to advise him on that one limited issue,” said Perrin. “We ceased to act on it many years ago.

“It is clearly to be distinguished, in my view, from assisting him in the purchase of a private jet. Under our policies as they have evolved since 2008, we would not now act for the likes of Obiang, even on an access-to-justice issue.”

He said Clifford Chance would be “initiating discussions” with other London law firms to coordinate a statement by the legal sector on tackling corruption.

The firm declined to address other allegations published by Private Eye, including that it tried to set up an offshore company for the daughter of Angola’s former president in 2012, and that it drafted a contract to transfer ownership of a broadcasting company to Saudi Arabia’s crown prince shortly after its executives were detained.

In 2011, US investigators accused Obiang of looting more than $100m from his country. He spent much of the money on luxuries including a gem-encrusted glove from Michael Jackson’s Bad tour. In 2014 Obiang agreed to relinquish more than $30m of assets to settle the case.

Equatorial Guinea is one of the most poverty-stricken countries in the world, despite its vast oil wealth. In 2011 half the population lacked clean water, and a quarter of children exhibited stunted growth, according to Human Rights Watch.