The Government’s spies are embroiled in another legal row after deleting evidence relevant to Kim Dotcom’s $6 million compensation case.

Crown lawyers told the tycoon that information he requested was ‘‘aged off’’ the Government Communications Security Bureau’s systems.

He is suing the foreign spy agency after it was found to have illegally spied on him as authorities gathered evidence in the run up to a raid on his home.

Dotcom’s legal team argue this is contempt of court as parties are obliged to save relevant material if litigation is pending.

However, Prime John Key yesterday said the law governing the GCSB requires ‘‘raw intelligence’’ to be deleted (or ‘‘aged off’’) once it is no longer relevant.

He said opponents to beefed-up spying powers, introduced last year, argued that the GCSB should not hold on to information.

‘‘The great irony is ...now people seem to be saying ...we should be holding on to data forever. But they are just trying to join dots that cannot be joined and confuse people. Mr Dotcom is completely and utterly wrong.’’

Key differentiated between ‘‘raw intelligence’’ and files created by the spy agency.

‘‘There aren’t files missing,’’ he insisted.

Dotcom’s lawyers had made a broad request for all relevant material, not just raw intelligence.

Crown Law, the Government’s lawyers, told his legal team: ‘‘Some communications have automatically aged off. We propose to include . . . those communications which are still recoverable’’, he said.

GCSB would not confirm when the relevant intelligence was destroyed, or for long it is usually retained.

The illegal spying on Dotcom came to light in mid-2012. The GCSB was asked by police to assist with the case in December 2011.

A spokesman stated there was no deliberate intention or instruction to destroy material related to the Dotcom case.

It was not clear yesterday why the GCSB could not retrieve the files from cloud storage facilities.

Dotcom said the destruction of material was contrary to a statement given by Key in February last year.

‘‘This is a spy agency. We don’t delete things. We archive them,’’ Key said in Parliament.

Key said he stands by that statement. He was answering allegations that GCSB had deleted footage of him discussing Dotcom at the agency’s headquarters.

The existence of any video of Key doing that has never been proved.

‘‘But if it had been there...that’s not raw intelligence and that would be archived forever,’’ he explained.

Labour’s associate security and intelligence spokesman, Grant Robertson, said ‘‘aged off’’ was a euphemism for deleted.

‘‘This may have serious implications for Kim Dotcom’s case.

‘‘More than that, it calls into questions claims John Key made in Parliament ... that the GCSB does not delete files.’’

Dotcom is battling extradition to the US on internet piracy charges.It also emerged last year that the GCSB had illegally spied on 88 Kiwis, prompting the controversial law change.