Liberal Democrat MP Norman Baker has challenged a blanket ban on access to MI5 files.

Baker used the Data Protection Act to apply for material held on him by the security services in July last year.

Baker is challenging a blanket ban on access to MI5 files announced by the government in response to his request. "This is not about me. It is about establishing a very important principle," Baker told ePolitix.com

The Lib Dem MP argues that the security services should be subject to the law - particularly on data protection issues.

"Each applications for information should be treated on its merits not greeted by a blanket exemption he said.

He accuses MI5 of double standards. "The security services have accepted that material can be released and they have released information to the public records office. But on the other hand they argue for blanket exemptions for those that make applications," he said.

Baker says he is not motivated by concerns about what the security services may or may not have on file about him - if they have anything at all. He argues that the principle is enough. "After, I made my application I was sent a letter, allegedly from an MI5 source, saying I had a file," he said.

The MP is appealing to the newly formed National Security Data Protection Tribunal on two counts. He will be represented in the landmark case by Andrew Nicol QC, Henrietta Hill - of Doughty Street chambers - and legal director of Liberty, James Welch.