Journalists at Guardian Media Group (GMG) will strike in December to protest the proposed sale of The Observer newspaper to Tortoise Media.
The industrial action will take place on December 4 and 12, following a National Union of Journalists (NUJ) vote where 93% of members supported the walkout.
Tortoise Media, led by former BBC and Times editor James Harding, has proposed investing £25 million in the broadsheet, and placing it behind a paywall, aiming for 173,000 subscribers.
However, GMG journalists have raised concerns about Tortoise’s financial stability, as the company has been loss-making since its 2019 launch.
The NUJ criticised GMG for recommending the sale before completing due diligence, calling for the process to be paused to address staff concerns.
The Observer is Britain's oldest Sunday newspaper.