More than two years into a campaign that has unionized more than 350 Starbucks stores, the company is facing mounting pressure from union officials and activists who say it has illegally retaliated against workers and resisted contract negotiations.

Starbucks, which denies violating labor laws, has responded with mixed signals about its willingness to engage with the union. The company announced early last month that it was seeking to restart negotiations at unionized stores, only one of which has held bargaining sessions over the past six months. Yet the company continues to resist a union demand that some workers be allowed to take part in bargaining sessions remotely to enable more to participate.

Starbucks has taken steps to address workers’ complaints about being overstretched in stores. But it and the union have sued each other in a dispute arising from social media postings about the war in Gaza.

A report on Starbucks’ labor practices, prompted by a shareholder vote and released last month, criticized the company for falling short on commitments it made to respect union activity, though it found “no evidence of an ‘anti-union playbook.’”