Police are investigating a break-in at the Auckland electorate office of Health Minister David Cunliffe.
Mr Cunliffe on Thursday would not comment on the burglary, other than to confirm that a complaint has been made to police.
The Diplomatic Protection Squad will not comment on the incident, but whoever broke into Mr Cunliffe's office stole either the hard drive or memory stick of the office computer, believed to contain confidential information of a political nature.
National leader John Key, who has accused Labour of infiltrating his party's annual conference, says he knows nothing about the break-in.
Trade Minister Phil Goff used question time in Parliament on Thursday to mock National's claim that Labour was behind the secret recording of its MPs at a cocktail party last weekend.
National has suggested Labour is responsible for the secret recordings made during National's party conference.
National has also suggested that Mr Key's rubbish has been interfered with at least twice.