Only 24 hours after another panel member quit, questions emerged over Professor Geoffrey Boulton because of his previous views that climate change is caused by human activity.

The investigation was set up to look into whether scientists at the University of East Anglia's Climatic Research Unit (CRU) covered up flawed data.

But some have cast doubt on whether the inquiry results can be trusted if Prof Boulton, general secretary of the Royal Society of Edinburgh, remains on the panel.

The leading geologist was one of five people chosen by former University of Glasgow principal Sir Muir Russell to carry out the high-profile investigation. A statement released at the launch of the inquiry on Thursday said none of the panel members had a "predetermined view on climate change and climate science".

It added: "They were selected on the basis they have no prejudicial interest in climate science."

However, The Scotsman can reveal that only a few months ago, Prof Boulton, from the University of Edinburgh, was among a number of scientists who, in the wake of the climategate scandal, signed a petition to show their confidence that global warming was caused by humans. And for at least five years, he has made clear his strong views on global warming. He has given interviews and written articles – including in The Scotsman – that have spelled out his firmly held beliefs.

In one article for Edinburgh University, he wrote: "The argument regarding climate change is over." And for 18 years, he worked at the University of East Anglia (UEA) – the establishment at the centre of the scandal.

Last night, on being questioned by The Scotsman, Prof Boulton insisted he was a "sceptical scientist" prepared to change his views "if the evidence merited".

The controversy follows the resignation of another panel member, Dr Philip Campbell, editor-in-chief of Nature magazine, just six hours after the inquiry launch. He stepped down after it emerged he had given an interview to Chinese radio about the climategate scandal, defending the behaviour of the scientists at the CRU.

Dr Benny Peizer, director of the Global Warming Policy Foundation, a think tank which claims the debate on climate change has become distorted, called for Prof Boulton to step down, too. He said: "Prof Boulton obviously is a very distinguished geologist. The problem is, he is a very outspoken campaigner on this issue and he's given talks calling for galvanising public opinion. He also worked at the very institution that he is now going to be investigating. That, we think, is a conflict of interest."

He said he was "speechless" about why Prof Boulton and Dr Campbell had been appointed in the first place.

"It looks like a shambles and it looks like the chairman of this panel hasn't really thought this through," he said. "Everyone must have told him (Sir Muir] that it's a very contentious issue and he should make sure the panel members have no bias at all."

He added that he thought it was "impossible" that Prof Boulton could remain in post.

The UEA, one of Britain's leading climate-change research centres, helps compile a global temperature record published by the Met Office. This data is used by the government to justify its targets for cuts in carbon emissions.

The university appointed Sir Muir in December to head an inquiry into a series of allegations over manipulated data.

Prof Boulton said he had been open about having worked at the School of Environmental Sciences at UEA between 1968 and 1986.

"Since then, I have had no professional contact with the University of East Anglia or the Climatic Research Unit," he said. He added that he had "declared my current view of the balance of evidence: that the earth is warming and that human activity is implicated. These remain the views of the vast majority of scientists who research on climate change in its different aspects".

But he added: "As a sceptical scientist, I am prepared to change those views if the evidence merits it. They certainly do not prevent me from being heavily biased against poor scientific practice, wherever it arises."

A spokeswoman for the inquiry said Sir Muir was "completely confident each member has the integrity, expertise and experience to complete the task."

Where eminent academic stands and what he's said in past

Dec 2009: In the wake of the scandal over leaked "climategate" e-mails, Professor Geoffrey Boulton signs a Met Office petition. It says: "We, members of the UK science community, have the utmost confidence in the observational evidence for global warming."

• Dec 2009: He gives an interview to The Scotsman in which he expresses his concern that public belief in climate change might be damaged by the scandal.

• Oct 2009: Writes an opinion piece for The Scotsman, in which he spells out the evidence that humans are responsible for climate change. It reads:

• Oct 2008: Is one of 18 scientists who write an essay about the likely impacts of climate change by 2050, commissioned by the David Hume Institute. He predicts melting icecaps causing "the potential demise of the Netherlands, Bangladesh and Kuwait, flooding of large areas of the US Gulf of Mexico, Florida, and east coasts of Myanmar, Thailand and north-east China".

In Scotland, "the Forth, Clyde, Moray and Solway lowlands were at risk".

Governments are guilty of "misplaced optimism" and being "too preoccupied by the credit crunch".

• 2005: In a paper produced for Edinburgh University's Annual Review, Prof Boulton is quoted as saying: "The argument regarding climate change is over."

• 1968 to 1986: He spends 18 years working at the School of Environmental Sciences at the University of East Anglia – the university at the centre of the scandal.

However, Prof Boulton does not work in the Climatic Research Unit.

HOTTING UP

THE "climategate" scandal broke just days before the Copenhagen climate change summit in December, when world leaders gathered to thrash out solutions to global warming.

A hacker obtained thousands of e-mails from the University of East Anglia's Climatic Research Unit (CRU) and posted them on a website. They appeared to suggest efforts by CRU scientists to cover up evidence that did not fit theories climate change was caused by humans. There was a reference to a "trick" to "hide the decline".

On Thursday, an inquiry into the scandal started, carried out by a panel led by former University of Glasgow principal Sir Muir Russell.

This inquiry will examine the quality of scientific practice by CRU researchers as well as investigating whether they complied with the university's freedom of information rules.

It will not examine the evidence on whether or not global warming is caused by human behaviour.