Amazon wrongly dismissed two workers last year who had demanded better working conditions during the pandemic, the U.S. National Labor Relations Board has found according to Ars Technica Tuesday.

Maren Costa and Emily Cunningham were designers at Amazon's Seattle headquarters and their conflict with management started in 2018 when they joined workers supporting shareholder petitions urging Amazon to do more to fight climate change.

Costa and Cunningham claimed Amazon imposed rules in a discriminatory way and had vague policies that "restrained" employees from exercising rights, based on a charge document obtained by Reuters.

The board told Amazon that if it failed to settle the complaints it would be charged with unfair labor practices. Such cases can result in injunctions, settlements or remedial orders.

The terminated employees and a handful of others rallied fellow workers to the cause. On Sept. 20, 2018, thousands of Amazon staff walked out in protest at the company's policies on climate change.

The group wrote an open letter, which was signed by more than 8,700 Amazon employees, to chief executive officer Jeff Bezos and the board of directors.

Lawyers told Costa, Cunningham and others that in criticizing the company, they had violated its policies that prohibit employees from talking about Amazon publicly.

"I don't regret standing up with my co-workers...In this crisis, we must stand up for what we believe in, have hope and demand from our employers a basic decency that's been lacking in this crisis," The Guardian quoted Costa as saying in a statement at the time of her termination.

For her part, Cunningham said Amazon "tried to silence workers and it hasn't worked. We're actually stronger than ever. Organizing continues to grow at Amazon."

According to the labor agency, the number of filings accusing Amazon of intervening with employees' right to organize had more than tripled during the pandemic.