The NHS is set to appeal to the House of Lords in a last-ditch attempt to stop the publication of child leukaemia statistics.

Officials in the NHS Common Services Agency (CSA) have opted not to accept a court of session ruling which ordered the body to hand over the secret data.

The legal move is the first time a public body has taken a freedom of information (FoI) dispute to the UK's final court of appeal.

The saga began when Michael Collie, a researcher for Green MSP Chris Ballance, asked the CSA in January 2005 for records of leukaemia in under-15s in Dumfries and Galloway.

He wanted to know if there were any cancer hotspots next to the Chapelcross nuclear plant or the Dundrennan military range. There have long been suspicions that clusters of the potentially fatal blood cancer could have been caused by radioactive pollution.

Plutonium from the Sellafield nuclear plant washes up on the Solway coast, and depleted uranium shells have been tested at the Dundrennan military range near Kirkcudbright. Scotland's oldest nuclear station, which is now being decommissioned, is at Chapelcross, near Annan.

The CSA, which is also known as NHS National Services Scotland, released limited details and the case ended up with Scottish Information Commissioner Kevin Dunion, who ruled in Collie's favour. The NHS body refused to hand over the data and appealed to the court of session, which dealt with the case late last year.

In a landmark ruling, the court rejected the CSA's arguments and found in favour of Dunion's ruling. Lord Marnoch said at the time that the FoI law "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."

However, despite their two defeats, the CSA is set for one final attempt at stopping the leukaemia statistics coming out. The NHS body has instructed its solicitors to appeal the court of session's decision. Such a move is likely to take months to be resolved and would probably drag the row out into its third year.

Green MSP Chris Ballance said of the CSA's decision to go to the Lords: "I am appalled, if unsurprised, that the CSA has decided to appeal this decision. They failed to convince the information commissioner of their case, and they failed to convince three eminent Scottish judges. Clearly they are now hoping that they will have better luck with the House of Lords, but if justice is to be done, the appeal will be thrown out."

A spokeswoman for the Scottish information commissioner said: "Our understanding is that the CSA is intending to appeal the court of session's decision to the House of Lords."

A spokesperson for the CSA 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."