Seven West Media chief executive Tim Worner said the company tumbled to a $994 million interim net loss after tax after writing down the value of its television, magazines and newspaper goodwill and other assets.

As foreshadowed by Fairfax Media, the company, controlled by Perth billionaire Kerry Stokes, wrote down the value of television goodwill by $961 million, goodwill associated with newspapers and magazines by $66 million and the book value of its newspaper mastheads and licences by $38 million.

The writedowns in part reflect the fact that Seven West Media shares have fallen by a third in the past year amid concerns about the state of the television advertising market and the performance of its West Australian Newspapers division.The regulator has asked companies to pay heed to their market value when conducting impairment reviews.

But Mr Worner told Fairfax Media that Seven's television performance is "exceptional" compared with its rivals Nine and Ten, and that the writedown did not dimish its belief in the future of free-to-air television, which contributes the lion's share of its profits and revenue and is facing structural challenges due to changing viewer habits.