Police have reportedly warned former Northern Ireland secretary Peter Hain that his computer may have been hacked.
Private detectives working for News International may have carried out the hacking using Trojan emails, the Guardian newspaper has reported, and other Northern Ireland civil servants may have been affected too.
A spokesperson for Hain described the issue as a "matter of national security". Hain was Northern Ireland secretary from 2005 to 2007.
The news comes as police expand their investigations into journalistic practices from phone hacking to computer hacking, and as stories swirl that other media groups may also be involved in similar acts.
News International has said it is fully co-operating with all police investigations.
Tom Watson, a member of the culture, media and sport select committee, told the Guardian: "Phone hacking is one thing, but targeting the computers of ministers with high-security clearance takes this police investigation to another level."