A Scottish NHS body which was ordered to reveal childhood leukaemia statistics under freedom of information law is to make a final appeal to the House of Lords in an attempt to keep the figures secret.

In the first case of its kind, the Common Services Agency (CSA) is to challenge a recent ruling by the Court of Session ordering it to hand over its records under FoI.

The CSA has resisted disclosure since January 2005, when Michael Collie, a researcher for Green MSP Chris Ballance, first asked for its records on leukaemia in under-15s in Dumfries and Galloway.

Mr Collie was trying to establish whether there were cancer clusters associated with Chapelcross nuclear power station and the Dundrennan military firing range, which tests depleted uranium shells.

When the CSA refused to comply, citing patient confidentiality, Mr Collie successfully appealed to the Information Commissioner.

The commissioner said the CSA could apply a statistical make-over to its raw data to enable it to preserve patient confidentiality.

When the CSA appealed against the commissioner's decision to the Court of Session late last year, its argument - that it was not obliged to create any new data - was thrown out by three judges. In the landmark ruling, Lord Marnoch stressed FoI should "be construed in as liberal a manner as possible."

"I do not see why the commissioner should not be accorded the widest discretion in deciding the form and type of information which should be released," he said.

The CSA has now instructed its lawyers to mount an appeal to the Lords, meaning the case will probably enter a third year. Mr Ballance said the CSA was wasting its time by appealing.

"I am appalled, if unsurprised, that the CSA has decided to appeal this decision.

"They have failed to convince the Information Commissioner of their case, and failed to convince three eminent Scottish judges. They are now hoping they will have better luck with the House of Lords, but if justice is done the appeal will be thrown out."

A CSA spokesman said: "We have been advised by counsel that we have grounds for appeal to the House of Lords, and in view of the fundamental principle at the heart of this matter - patient confidentiality - we have decided to proceed with this appeal."

The Information Commissioner's office confirmed it was aware of the appeal.