Simon Hughes has condemned the practice of hacking in to telephone message systems after a man pleaded guilty to intercepting the MP's voicemail.
Mr Hughes was speaking after private investigator Glenn Mulcaire pleaded guilty at the Old Bailey to five charges of unlawfully intercepting voicemail messages left for public figures including the North Southwark and Bermondsey MP and others including Max Clifford and model Elle Macpherson.
Mulcaire was in the dock with News of the World royal editor Clive Goodman. Both men pleaded guilty to conspiracy to intercept telephone calls "without lawful authority" between November 1 2005 and August 9 2006.
Through his barrister Mr Goodman apologised to members of the Royal Family whose messages he admits to intercepting.
"Intercepting personal voicemail messages is a completely unacceptable breach of privacy – whether the victim is a royal prince, a politician, or someone completely out of the public eye," says Simon Hughes.
"People who leave messages and those intended to receive them are all entitled to have private conversations. We live in an age where invasions of privacy are becoming more frequent. This does not make the practice any more acceptable.
"Tapping phones or intercepting messages should only be done with the authority of the law in the most exceptional cases and in the public interest. Tracking down terrorists is the obvious topical example.
"I hope that all newspapers, and journalists more widely, and all their representative bodies will now confirm that this practice is unacceptable and that nobody else will have their privacy invaded in the same way.
"I have long held the view that courts should be allowed to deprive those responsible for this sort of behaviour of their liberty because it is a serious offence to interfere with the freedoms of others.
"Some people, like me, are resilient enough to take this sort of behaviour more or less in their stride, but other people are not, and nobody should have to."
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