The separation of billionaire power couple Andrew and Nicola Forrest has caused acrimony between Nine's Australian Financial Review and rival Seven West Media newspaper, The West Australian.

Sources at Nine say it had the story about the Forrest split exclusively but it was taken by The West Australian from the AFR's newspaper before it had been publicly released. SWM prints the AFR for the WA market at its Herdsman headquarters, with no other commercial newspaper printing option now existing in WA.

The AFR says it sent questions to the Forrests' private investment group, Tattarang, after Dr Forrest revealed to the Australian Stock Exchange that he had transferred 50 million shares in Fortescue Metals Group to Nicola Forrest's company, Coaxial Ventures.

In response, Tattarang provided the AFR with a statement confirming the couple had separated and the transfer was part of that separation.

Given the importance of the story, the AFR decided not to publish the online version of its newspaper until well after all other major Australian newspaper deadlines had passed.

The electronic files for the printing of the newspaper were sent to SWM's printing press, which is located alongside The West Australian in Herdsman, about 5.30pm on Wednesday.

It is understood The West Australian made calls to Tattarang's media team on Wednesday afternoon, though it is not known whether those calls were made before or after 5.30pm.

The Australian Financial Review became aware that The West was onto the story and published it online at 6.03pm. The West Australian published the story on its website at 6.04pm.

AFR editor-in-chief Michael Stutchbury told Business News the Nine masthead had broken the story and The West had sourced it from "I wonder where".

"Big scoop by The West Australian! Not," he said.

"The Financial Review published the full exclusive story by Peter Ker and Brad Thompson - and the critical financial transaction behind it - on afr.com at 8:03pm Sydney time.

"The West ran a rushed, bare-bones, first-take 'exclusive', sourced from 'I wonder where', a minute later."

In an article published yesterday in The West Australian, the newspaper claimed to have first asked questions of Tattarang about the couple "effectively living separate lives" in December. 

West Australian Newspapers editor-in-chief Anthony De Ceglie said it sounded as though the AFR was just "having a whinge". 

"Or maybe they're upset our front page looked so much better than theirs," he said.

"The real question is how did the AFR know The West Australian was about to publish a story on the planned statement from the Forrests? It could have only happened, in my opinion, if their 'exclusive' was done arm-in-arm with the Forrest publicity machine."

The stoush has also highlighted concerns around SWM's newspaper printing monopoly in Western Australia, with sole competitor IVE Group closing its doors in May.

SWM's suburban competitors at POST Newspapers, Perth Voice, Examiner Newspapers and Fremantle Herald are now all printed by SWM while national newspapers the AFR and The Australian are also printed at Herdsman. The Business News magazine was printed by IVE, but is now printed by Vanguard Press.

Adding further intrigue to the issue is the ongoing feud between billionaire Kerry Stokes, who controls SWM, and Dr Forrest. Business News revealed in February that Mr Stokes was upset that Dr Forrest's Fortescue Metals Group had given a truck supply contract to German company Liebherr, rather than the Stokes-controlled WesTrac. Dr Forrest accused Mr Stokes of using The West Australian to retaliate.

POST Newspapers owner and editor Bret Christian said it would have been preferable for newspaper proprietors if there had been more competition in the newspaper printing sector.

He said he had held talks with SWM before signing a contract to have his newspapers printed at Herdsman and had received verbal guarantees that security procedures were in place to ensure nobody from outside the press could access them.