WA premier against Seven West acquisition

Premier Colin Barnett would prefer Western Australia's main news organisation doesn't take over Rupert Murdoch's The Sunday Times.

The planned acquisition of the Sunday newspaper and its online news website PerthNow by Kerry Stokes' Seven West Media is being assessed by the Australian Competition and Consumer Commission.

"I would prefer it didn't happen - I think diversity in media is important and clearly with Channel Seven and The West Australian being one, there's a lot of cross-over," Mr Barnett told ABC radio on Thursday.

ACCC chairman Rod Sims said the competition watchdog invited feedback on the proposed transaction by August 18.

A decision is expected on September 15.

"There will be some saying `this is just two players going into one', there will be some saying `don't worry about it. There's so much different sources of news out there and other content that it doesn't matter'," he told the broadcaster.

"And so our fun job is to balance those two conflicting opinions."