Leading experts involved in the World Health Organisation's decision to declare a flu pandemic on Wednesday rejected accusations of undue influence from the pharmaceutical industry.

The heads of panels of scientists advising the agency on vaccines and the alert said "meticulous care" was taken to avoid conflicts of interest and to keep a distance from industry as far as possible.

David Salisbury, of the WHO's standing Strategic Advisory Group of Experts (SAGE) on immunisation, said candidates for the body were vetted before they joined and those with conflicts of interest were excluded.

"There has been no declaration of conflict from any SAGE member in our proceeding on A (H1N1) vaccine," he told a probe investigating the international response to the pandemic.

Salisbury is director of immunisation at Britain's Department of Health.

SAGE gave decisive technical advice to WHO Director General Margaret Chan last year on whether or not to produce a special vaccine for the A(H1N1) virus, the timing of production and vaccine needs.

Parliamentarians conducting a Council of Europe probe have criticised the transparency of decision-making during the pandemic and especially the potential influence of the pharmaceutical industry on vaccination.

Governments have sought in recent months to cancel mass orders of hundreds of millions of dollars worth of swiftly developed special pandemic vaccines after fears about the severity of swine flu died down.

Salisbury said pharmaceutical industry representatives were invited to take part in a SAGE consultations dealing with vaccine production capacity and development.

"To my knowledge the industry has not done anything other than provide us with scientific information," he said.

"There was at no time any attempt to influence the advice we gave, either in the timing or the content of the advice we gave."

Australian infectious disease expert John Mackenzie, head of the WHO's Emergency Committee of scientists, also defended their safeguards.

"Certainly as the chair I was not approached by the pharmaceutical industry and I don't know of any member who was," he said.

"I was the only person known externally so who could have been approached," he added.

His body recommended an international emergency over the new flu virus and the declaration of a pandemic last June.

Mackenzie said the secrecy surrounding the identities of the other members of his panel and their work was precisely aimed at protecting them from commercial or state pressure.