Facebook deliberately used an over-zealous blocking system that took down the pages of Australian emergency services last year as a negotiating tactic, whistleblowers claim.
The social network moved to block all news outlets in Australia over a row about paying news providers.
But fire services and state health services were also blocked, during fire season and Australia's vaccine rollout.
Facebook says blocking other pages had been an honest mistake.
Former employees, backed by the Whistleblower Aid charity, say the company intentionally "over-blocked" Australian pages at a critical time to gain leverage over the Australian government.