The National Labor Relations Board will file a complaint accusing Alphabet Inc’s Google of unlawfully monitoring and questioning workers, who were fired for protesting against company policies and trying to organise a union.

This was revealed by former employees who were fired for protesting against the company.

Google said it was confident in its legal position.

“Google has always worked to support a culture of internal discussion, and we place immense trust in our employees,” it said.

“Actions undertaken by the employees at issue were a serious violation of our policies and an unacceptable breach of a trusted responsibility.” it added.

The complaint follows a year-long investigation prompted by a petition by five people fired by Google after they led efforts to protest company policies and organize colleagues into a potential union.

The Communications Workers of America union helped author the workers’ charge.

Google said the workers breached information security rules.