Its president is known as one of the most despotic in Africa, his heir stands accused of squandering millions of public funds on Michael Jackson memorabilia and the majority of its people live on less than $2 per day.

Yet Equatorial Guinea this week finds itself in the unlikely position of playing host to a human rights conference on how to improve life for ordinary Africans.

The US-based Leon H Sullivan Foundation – originally known for its goal of "advancing the cause of the underprivileged" – is hosting its biennial summit in the west African country, much to the dismay of civil rights activists.

More than 4,000 delegates, flown in on two specially chartered planes, will enjoy the five-star facilities at Equatorial Guinea's luxurious £500m Sipopo resort – a 3m-square-metre development featuring a private mile-long artificial beach, 52 beachfront villas, an 18-hole golf course and the country's first spa – while discussing "critical issues in human rights" including food security, freedom of the press and education.

"To describe the Sullivan summit as a 'human rights gathering' is a perversion of meaning and language. They celebrate one of Africa's worst human rights violators," said Thor Halvorssen, president of the US-based Human Rights Foundation. "To add insult to injury they do so from a petro-fuelled billion-dollar conference centre, while two thirds of the country languishes on less than $2 per day. It is breathtaking hypocrisy at its worst."

The willingness of the international community, including the Sullivan Foundation, to engage with Equatorial Guinea is seen by many as a triumph of PR rebranding, an increasingly popular tool for dictatorial African regimes.

Equatorial Guinea – sub-Saharan Africa's third largest oil producer with over 270,000 barrels a day – has long been recognised as one of Africa's most repressive regimes. The country is ranked 172nd out of 182 nations by the anti-corruption watchdog Transparency International, the fifth most censored country in the world by free press group the Committee to Protect Journalists, and described as one of the "worst of the worst" human rights abusers, alongside North Korea, Somalia, Sudan and Syria, by the US human rights group Freedom House.

But Teodoro Obiang Nguema Mbasogo, Africa's longest serving head of state, has enjoyed what critics describe as an "image makeover" since enlisting the help of powerful Washington DC lobbyists.

Bill Clinton's lawyer Lanny J Davis, who also represented the former Ivory Coast president and war crimes indictee Laurent Ggagbo, and the PR firm Qorvis Communications, which also represents Bahrain, Sri Lanka and Saudi Arabia, have both received millions of dollars for representing Obiang's regime.

Their efforts are credited with the decision to allow Equatorial Guinea to co-host the high-profile Africa Cup of Nations this year, while in July Unesco decided to award a research prize funded by Obiang, despite strong criticism from human rights organisations.

Reports by the US Senate in 2004 and 2010 found that millions of dollars of Equatoguinean oil income had been deposited in private bank accounts in the US, Spain and Luxembourg, prompting investigations by the US justice department and authorities in France and Spain.

Last year the US authorities began efforts to seize $70m (£44m) worth of property belonging to Obiang's notorious son and vice-president, Teodorin Nguema Obiang Mangue, whose assets include a $30m mansion in Malibu, a $38.5m Gulfstream jet, and more than $2m in Michael Jackson memorabilia.

In France – where Teodorin is subject to an arrest warrant – police recently seized 11 luxury cars belonging to the 41-year old, including two Ferraris, two Maseratis and a Rolls-Royce, as well as a €40m (£32m) Paris mansion with a disco, spa room, hair salon, gold and jewel encrusted taps and balcony views of the Arc de Triomphe.

The use of PR companies by African governments to deflect attention from controversial or illegal activities is a growing phenomenon, experts say.

"Many African governments used Washington-based lobbyists," a source at one DC-based consultancy said. "They might use one for tourism, another for the oil industry and another for trade and investment opportunities. Their role is to get access to policy makers and key government officials right up to the president, and build better public relations in the US.

"You might think that is the job of embassies, but diplomatic missions just don't have that level of strategic relations with very senior people in the government and private sector," the source said.

In the case of Equatorial Guinea, it has emerged that the country is part of a complex web of cash and influence which links the Obiang regime with the US civil rights movement and highly paid US-based lobbyists.

At the centre is Hope Masters – daughter of the late Leon Sullivan and current CEO of the Sullivan Foundation. Under her leadership the Sullivan Foundation has accepted money from the government of Equatorial Guinea, according to President Obiang, who stated publicly last December that "Equatorial Guinea contributes today in the financing of [the] Leon H Sullivan Foundation, as it has been doing in the past."

Masters is married to the well-known Washington lobbyist Carlton Masters, the co-founder of GoodWorks International, which represents several African governments with poor human rights records including Angola, Rwanda and Cameroon.

The other founder of GoodWorks, Andrew Young, is a well-known elder of the US civil rights movement and friend of Martin Luther King, and was until recently chair of the board of the Sullivan Foundation.

Critics allege that the Sullivan Foundation has traded its human rights principles for cash and used its summit to attract business for GoodWorks.

"Mrs Masters is married to a Washington lobbyist who has traded in his civil rights legacy to represent some of Africa's most dangerous leaders," said Halvorssen. "Their work in Equatorial Guinea is so obviously an attempt to burnish the credentials and cover up 30 years of human rights violations by Obiang and his family. It is a level of venality that is unseen in recent history by a foundation that had credibility in Washington DC."

The Sullivan Foundation declined to comment on the links between the summit and Washington lobbyists, but it has responded furiously to public criticism of its decision to continue working in Equatorial Guinea.

"For several months, the Leon H Sullivan Foundation has been under news, Twitter and blog attacks by journalists and vocal 'human rights organisations' who have used smear tactics and yellow journalism to undermine the upcoming ninth Leon H Sullivan summit," Masters said in a recent statement. "These organisations use the politics of destruction and cheap buzzwords to bring attention to themselves without fact checking or simple truth verification of their outrageous claims of ongoing abuse and corruption."

But in a new twist that has put even more pressure on the embattled Sullivan Foundation, even some associated with the conference have expressed concern about the human rights situation in Equatorial Guinea.

A spokesperson for John Kufuor, the former president of Ghana, who is co-chairing the conference, said Kufuor had decided to attend despite his own misgivings about the Obiang regime.

"President Kufuor understands the argument that people have against the conference," his spokesperson said. "He decided to attend, on the basis that he will make certain things known to Obiang which are part of the important democratic transition in that country. He recognises that there are major problems in Equatorial Guinea, including the lack of basic freedoms and rights."

The conference takes place exactly two years after Obiang's government executed four political dissidents, who civil rights groups say were kidnapped in Benin and convicted in a summary military trial based on confessions extracted by torture.

One group that works to help political dissidents in Equatorial Guinea says that a former associate of Teodorin, Florentino Manguire – who has been repeatedly jailed without charge in the country – was re-arrested shortly before the Sullivan summit and released on the first day to avoid embarrassment.

"The Sullivan Foundation should invite Florentino Manguire, who was recently unjustly imprisoned, or the families of the four men kidnapped in Benin, repatriated, tortured and executed after a sham trial, to talk on the travesty that is the justice system in Equatorial Guinea," said Tusantu Tongusalu, the director of Equatorial Guinea Justice.