More than 225 Google engineers and other workers have formed a union, the group revealed on Monday, capping years of growing activism at one of the world’s largest companies and presenting a rare beachhead for labour organisers in anti-union Silicon Valley.

The union’s creation is highly unusual for the tech industry, which has long resisted efforts to organise its largely white-collar work force. It follows demands by employees at Google for policy overhauls on pay, harassment and ethics, and is likely to escalate tensions with top leadership.

The new union, called the Alphabet Workers Union, was organised in secret for the better part of a year and elected its leadership last month. The group is affiliated with the Communications Workers of America, a union that represents workers in telecommunications and media in the US and Canada.