Former Liberal minister Chris Hartcher is alleged to have run an ''off the grid'' computer network in his electorate office before the 2011 state election - a period being investigated as part of a major corruption inquiry.

A source familiar with Mr Hartcher's office has said the then shadow cabinet minister bought computers that were installed in his electorate office at Erina on the Central Coast.

Elaborate network: Chris Hartcher said he feared his email was being monitored. Credit:Sasha Woolley

The source said there was one computer connected to the official parliamentary network but that ''every other computer in the office was a computer that was bought by Chris Hartcher and worked on a separate network''.

Mr Hartcher's explanation was that he feared his email and other data could be monitored by ''Labor cronies'' due to the party being in government at the time, the source said.