The scientists whose leaked emails sparked a heated debate and speculation over the quality of research into climate change have been cleared by an independent inquiry in Britain.

The six-month inquiry cleared the climate scientists of accusations that they manipulated their data, but criticised them for being too secretive and defensive about their research.

It was alleged the researchers abused their positions to cover up flaws and distort the process that determines which scientific studies are published in journals and subsequently enter the official records.

But the inquiry panel said it had not found any evidence of behaviour that might undermine the conclusions of the Intergovernmental Panel on Climate Change.

It is the third inquiry into the email affair, dubbed 'Climategate', and clears the head of the Climate Research Unit at the University of East Anglia and his colleagues of the most serious charges.

The panel did criticise the scientists for not being open in how they responded to requests for information from outside the scientific community.

When 13 years of emails from scientists at the University of East Anglia's Climatic Research Unit were hacked into and released online last year, the ripples spread around the world.

Climate change sceptics seized on the emails to argue the scientists were manipulating and suppressing their data to support predetermined theories on man-made climate change.

Professor Edward Acton, from the University of East Anglia, says the findings "show there was ... absolutely nothing to hide."

The inquiry concludes the scientists' rigour and honesty are not in doubt and they did not subvert the peer review process to censor criticism.

But Sir Russell Muir, who led the investigation, says their work could have been more transparent.

"The question that arises was openness in relation to how that science was then being challenged, being discussed, and the commerce that there was between them and critics and critics and challengers right round the world," he said.

Also criticised was a graph prepared for the World Meteorological Organisation, showing temperatures from 1850 ticking up sharply at the end of the 20th century.

The inquiry found the graph was misleading, but not intentionally so.

The findings have not quelled the mistrust of climate change sceptics like Lord Nigel Lawson, from the Global Warming Policy Foundation.

"For scientists to be misleading the public and misleading the politicians on an issue where huge decisions, huge expensive decisions are going to be based on this, that is very disreputable," said the former British chancellor.

"The lack of openness is disreputable - the failure to acceed to freedom of information requests is disreputable."

'Attitudes have changed'

Douglas Keenan, an independent campaigner for accountability in science, argues the inquiry was not thorough.

But he says openness in the scientific community has improved in the wake of Climategate.

"There's no question that attitudes have changed and not just at the University of East Anglia," he said.

"I have also had requests based on the UK Freedom of Information Act ... for example Queens University Belfast, and I have noticed a marked change in their attitude and manner since all of this has happened."

Bob Ward, from the Grantham Research Institute on Climate Change at the London School of Economics, says Climategate might make it harder to recruit researchers.

"To be put under that kind of scrutiny is very difficult and I think some researchers will think long and hard about the extent to which they are willing to be identified as public individuals," he said.

"Some of these people get abusive emails - they're attacked publicly.

"It is not the kind of thing that I think anybody would relish."

The inquiry might be over but the debate about global warming continues with researchers' methods firmly under the microscope.