The government is pursuing former intelligence official Cameron Gill as the alleged source for a story by News Corp journalist Annika Smethurst which revealed a secret proposal to expand the powers of electronic intelligence agency the Australian Signals Directorate.

Court documents confirm authorities believe Mr Gill leaked classified information to Smethurst for the April 2018 story which triggered an investigation and an Australian Federal Police raid on the journalist's home earlier this year. Police also executed a warrant at Mr Gill's house in September but have previously refused to confirm the reasons for the raid.

News Corp journalist Annika Smethurst, whose home was raided by federal police. Credit:Dominic Lorrimer

Smethurst, who is currently mounting a challenge in the High Court to prevent police from using the material seized from her home, has never identified her source. In a statement on Thursday, a spokesman for News Corp said: "Annika has never revealed her source publicly, privately, nor to her employer and we are not going to ask her."

The warrant for the raid on Gill's house, contained in documents filed to the court, states: "Between 1 February 2018 and 29 April 2018, Cameron Jon Gill being a staff member of the Australian Signals Directorate communicated Australian Signals Directorate information to Annika Claire Smethurst contrary to section 40 of the Intelligence Services Act 2001."