Nine Entertainment Co has refuted claims that its chairman Peter Costello secretly worked as a lobbyist for casino giant Crown Resorts when it was controlled by billionaire James Packer.

In a series of leaked emails revealed by The Australian newspaper and sent to a number of Nine employees including Costello and Nine Publishing managing director James Chessell, Packer alleged Costello worked as a “secret Crown lobbyist” in 2011 and “should resign” from all public positions.

A Nine spokesperson said Costello was never employed as a Crown lobbyist and said, “Peter Costello was an adviser to Consolidated Press Holdings in 2011, for a year”. Consolidated Press Holdings is one of Packer’s private investment vehicles, which housed its shares in Crown alongside other assets.

Packer ended his 20-year involvement with Crown Resorts as its largest shareholder earlier this year, when he sold his stake in the company to private equity firm Blackstone. The sale came after a 2019 investigation by this masthead led to a NSW inquiry that found the company was unfit to open its new Sydney casino.

Costello joined the board of Nine in 2013. He was appointed chairman of the media company in 2016. Nine Entertainment is the owner of The Sydney Morning Herald and The Age.

The Packer family owned the Nine Network between 1956 and 2007. James sold the then television company to private equity firm CVC for about $5 billion.

In a note sent to staff on Monday, Nine Publishing’s managing director James Chessell said he was reluctant to comment publicly on The Australian report due to “mental health sensitivities.”

“I’ve received a blizzard of correspondence from Packer since he took exception to something we published in late June. After trying to engage with him at first - which clearly didn’t work - I’ve ignored almost all of it,” Chessell said.

“I never heard a word from Peter Costello about Crown Unmasked before, during or after publication/broadcast.