A group of Tesla workers trying to form a union in New York state has accused the company of firing more than 30 people to try to quash the campaign.

Organisers in Buffalo said the staff were sacked a day after the union went public with its efforts.

"I strongly feel this is in retaliation to the committee announcement and it's shameful," said Arian Berek, a fired member of the organising committee.

Tesla did not respond to a request for comment.

The electric car firm is led by billionaire Elon Musk, who has been outspoken about his opposition to unions in the past.

In the complaint filed with government labour officials, the union cited 18 people it said the company had fired "in retaliation for union activity and to discourage union activity".

Organisers said, based on a company chat, they believed more people had been fired and expected to add names to the complaint. They said they were still confirming how many of those fired had been directly involved in the campaign or had just indicated their support.

The Buffalo facility employs about 2,000 people, according to organisers from Tesla Workers United, which is backed by the same union that launched organising efforts at Starbucks.

The group is now seeking support from Tesla workers in Buffalo to hold a vote about joining a union. It sent a letter to the company on Tuesday outlining its plans and asking leaders to agree to ground rules for a "fair" election.

A day later, campaigners said, Tesla fired more than 30 workers and sent an email informing staff of a policy that bars recording of workplace conversations without the consent of all parties.

Organisers said the rule violated their rights under federal and state laws.

The National Labor Relations Board has previously found that Tesla violated labour rules during an organising effort at its car manufacturing plant in California.

"We're angry. This won't slow us down. This won't stop us. They want us to be scared, but I think they just started a stampede," said Sara Costantino, current Tesla employee and organising committee member.