Kevin Rudd's repeated claims of systematic anti-Labor bias in his treatment by News Corporation newspapers ahead of the September election were fuelled by an independent assessment of media reporting commissioned by the Labor Party.

The revelation underlines the extent of frustration within the government as it reeled from its bitter leadership instability and the late switch to Mr Rudd, whom many in the ALP had openly criticised.

Subject to media bias: Kevin Rudd. Credit:Wayne Taylor

The previously confidential study, obtained by Fairfax Media, was undertaken at the request of Mr Rudd's key adviser, Bruce Hawker, as the pair wrestled with what to do to rebuild the former prime minister's reputation and improve Labor's poor communication with voters in time for an election due within weeks.