Journalists at the Guardian, Observer and theguardian.com have voted in favour of possible industrial action, including a strike, should the company's £7m cost-saving measures lead to compulsory redundancies.

More than 80% of National Union of Journalists (NUJ) members who took part in the ballot voted for the option of strike action, should Guardian News & Media proceed with compulsory redundancies.

A total of 345 journalists at GNM – which publishes the Guardian, Observer and theguardian.com website network, including MediaGuardian – said they were prepared to strike (81.6% of the 424 ballot papers returned), and 374 said they would take action short of a strike (88.4%).

The company is looking to cut about 100 posts out of an editorial staff of 642. Just over 30 staff took voluntary redundancy in the autumn, and it is understood that up to another 30 have applied to the VR scheme since then.

GNM and the NUJ are in ongoing negotiations to come up with alternative cost-saving measures, including further voluntary redundancies, to avoid compulsory layoffs.

The NUJ general secretary, Michelle Stanistreet, said: "This overwhelming vote for action is not just about saving jobs, it is about journalists who are proud of the quality of newsgathering and writing in their papers and do not want to put it at peril."

A GMN spokeswoman said the company was in ongoing talks at Acas with the NUJ and was hopeful of resolving the dispute through negotiation.

The NUJ deputy general secretary, Barry Fitzpatrick, said the union had suggested a series of cost-cutting measures, including cuts to executive pay, job sharing, and more part-time working. He added: "The management has taken a serious risk of jeopardising the culture within the Guardian by trying to force through compulsory redundancies."

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