The International Policy Network, once the most persuasive and active think tanks campaigning against climate change science, has disbanded in the UK after what appears to be a split between its leading members.

A document released following a Freedom of Information request shows that the charity’ s chairwoman Linda Whetstone and her brother Michael Fisher held a private meeting in which they agreed to abandon the name of IPN UK after more than a decade. The meeting, held by telephone in November 2010, was perfectly within the charity's rules.

The minutes of the meeting, which cover a single side of an A4 sheet of paper, were obtained by The Independent this week and reveal that Whetstone also resigned from the board of the International Policy Network in the United States, despite being a leading member of the organisation.

This newspaper has also confirmed that Professor Julian Morris, a founding director of the IPN UK and US, is no longer a paid employee for IPN US where he was earning $137,000; he works for the US organisation on a part-time and voluntary basis as its president. He is now vice president for research at a rival think tank, the Reason Foundation.

Professor Morris, after speaking at a meeting on Wednesday, June 15 being held by a new think tank called the Legatum Institute, said: “The IPN is scaling down. There were two organisations, the IPN US Inc and IPN UK and now the two organisations are pursuing independent paths."

Asked whether the IPN had split over climate change, he added: “It is a long and complex story. It is what it is. I can see where you’re going with this.”

The closure of the free market IPN follows years of controversy about Exxon funding, alleged links to the tobacco industry and contested claims about Aids and the pesticide DDT.

It is possible, however, that the closure may be linked to family connections involving David Cameron that meant IPN could no longer exist as a major force of climate denial.

Whetstone is the mother-in-law of Steve Hilton, who is the director of strategy for the prime minister and was godfather to his son Ivan. Hilton is the man who persuaded the Conservative leader to adopt a robust stance on climate change and hug Huskies on the Norwegian glacier to illustrate his commitment.

Hilton’s wife, Rachel Whetstone, is a vice president at Google for communications, which has donated millions to climate change causes, including creating 21 Google Science Communication Fellows.

Linda Whetstone and her brother Michael, the trustees present at the private meeting, are the children of Sir Anthony Fisher who was an ideological disciple and former student of the father of neoliberalism, Friedrich Hayek. Fisher senior masterminded the global network of neoliberal think tanks, including setting up more than 150 organisations himself.

The launch of the International Policy Network’s publication Adapt or Die was reported in November 2004. The charity claimed climate change was a myth, that sea levels were not rising and that global warming would benefit humans by increasing fish stocks.

At that time Dr Roger Bate was also a director of the IPN. Morris and Bate were both named in a letter asking the tobacco company RJ Reynolds for £50,000 in funding for a book about the “myth of scientific risk assessment” which would deny the effects of passive smoking.

Morris denied involvement, but a book titled What Risk? edited by Bate was later produced in which Bate acknowledged Morris for his support.

The IPN name soon became associated with ExxonMobil after the American oil giant revealed in its own publications that it granted almost £250,000 ($400,000) to the IPN in the US between 2003 and 2006. An examination of IPN UK accounts registered at Companies House revealed that from 2003 to 2005 the US think tank in turn granted £204,379 to the IPN in London.

Exxon stopped funding the IPN following a letter in 2006 from Bob Ward who was then at the Royal Society calling on the world’ s largest seller of fossil fuel to stop funding organisations that were actively spreading misinformation about the science of human forced climate change. Ward is now at the Grantham Institute at the LSE in London.

An IPN statement at the time said: “The implication that IPN is somehow being funded by Exxon to promote ‘climate change denial’ (per the Guardian’s salacious headline) is preposterous nonsense. IPN’s founder and executive director, Julian Morris, has personally been involved in the climate change debate since writing his undergraduate thesis on the subject in 1992 and neither his views nor those of IPN have ever been influenced by any financial contributor.”

Until its dissolution the IPN has been central to the climate change denial machine. While receiving funding from Exxon, the organisation launched Adapt or Die in Washington in 2004 and published two further climate change books in time for the COP-10 meeting held that year in Argentina.

The IPN also attended the inquiry into the economics of climate change held by the House of Lords economic affairs committee, which was attended by Lord Lawson. Lawson claims in his book, Memoirs of a Tory Radical, that he began to question the science of climate change during the hearings. He would then go on to form the sceptic Global Warming Policy Foundation.

The think tank also established and launched the Civil Society Coalition on Climate

Change which, it claims, included 40 other organisations around the world. The IPN then “ coordinated participation of CSCCC members” at the UN climate meeting in Bali in 2008, distributing hundreds of copies of its report to delegates, participants and journalists for free.

The IPN was launched when the UK charity Atlas Economic Research Foundation, which was founded in July 1971, became part of the international network. During its existence the London office of the think tank raised more than £2.5million from donors. The organisation will continue in some form under the name Network for a Free Society.

Despite repeated attempts to contact her Linda Whetstone was unavailable for comment.