The inquiry heard first from Dr John Constable, Director of Policy and Research for the Renewable Energy Foundation, an independent charity which provides data and information about renewable energy technologies.

He appeared on behalf of Save Northumberland's Environment, which asked him to re-examine data provided by npower renewables about the claimed benefits for the proposed turbines.

It included projected carbon dioxide savings and energy generation levels.

But presenting his findings, he said: "Having reviewed npower's claimed benefits in the light of knowledge current at the time at which the Environmental Statement was written, and in the light of subsequent information, I conclude that they are significantly exaggerated, and should be revised downwards.

"The statements of benefit are inadequately demonstrated, significantly overstated, or presented in ways likely to mislead."

Dr Constable was particularly critical of the company's predicted energy yields - around 27.3 per cent - which he said was not based on site-specific measurements of wind resource, but on a national average.

He said: "This does not amount to site specific demonstration, and fails to satisfy the requirements of government guidance.

"In regard to energy generation quantifications, I find that npower's statements are couched in terms likely to lead to inaccurate inferences of significance."

Dr Constable also poured cold water on claims made in the ES that the wind farm would generate enough power to supply 27,000 local homes, adding it was unlikely that Middlemoor would perform as well as npower anticipated.

"It is important that the available capacity space for wind energy is not occupied by sub-optimal wind sites," he said. "It is still not obvious that Middlemoor is a suitable location.

"In point of fact, the applicants have not provided evidence to demonstrate the energy generation benefits, and what evidence is available does not support the view that the Middlemoor site is even a nationally mediocre location."

Dr Constable was followed by town and country planning expert Steve Arnold, who was also called by SANE to examine planning policy.

He said: "To the extent that national policy ascribes significant weight to the wider benefits of renewable energy developments, then it is essential to undertake a proper evaluation of the benefits, to be balanced against the harm which the proposal would cause.

"Drawing on the evidence of Dr Constable, it is evident to me that the actual contribution that this proposal will make to renewable energy objectives will be insignificant, and that the benefits claimed by the applicant are significantly exaggerated.

"These factors should be weighed against the sacrifice of a valued and valuable landscape to an alien form of development."

Mr Arnold added that npower had underestimated and downplayed the impact on the landscape and heritage, as well as residents, and the potential loss to the tourist industry.

He said: "The proposals conflict with the development plan, and there are no considerations which point to a decision being made contrary to the development plan.

"The Middlemoor proposals should be refused."

Report: Inquiry Day 7 Afternoon