DNA testing web site Ancestry has begun legal action to access millions of family records held by National Records of Scotland (NRS).

The Scottish government body has refused to enter into a financial agreement to provide access to more than 400 years of birth, death and marriage records.

Ancestry - the world's largest commercial genealogy website - operates on a subscription model, while NRS records are publicly available for a small fee.

At a hearing held in London, NRS said granting Ancestry access would cost £3.7m a year in lost income and be "catastrophic" for its finances.

The NRS archive includes about 25 million images and 98 million index entries.

According to a report in The Times, the Information Commissioner withheld the release of records under legislation covering the re-use of public sector information.

Ancestry's appeal against the Information Commissioner's notice was partly upheld at a tribunal.

But it was told a further hearing would be required to decide on whether the records could be released.

'Severe impact'

Janet Egdell, former interim chief executive of NRS, told the tribunal: "Allowing re-use would result in additional cost both in financial and human resources for NRS.

"This was expected to have a severe impact on the income stream of NRS and its ongoing ability to carry out its public function."

The NRS holds Scottish records spanning the 12th to the 21st centuries and is responsible for the registration of life events such as births, deaths and marriages, as well as the country's census.

It also regularly provides reports on the Scotland's population, as well as drug deaths and other significant moments affecting the country and its residents.

Ancestry's request excludes birth records after 1921 and deaths after 1971.

It said this would "protect the privacy of individuals whose personal data is contained in any of the categories".

In a statement Ancestry said: "We are reviewing the tribunal's ruling carefully and will determine our next steps in due course."

NRS said it would be "inappropriate" to comment on live legal action.