Last week, Google agreed to let the U.S. Department of Defense use its Gemini AI models inside classified military networks for “any lawful purpose,” a deal critics say could open the door to autonomous weapons and mass surveillance of American citizens with few enforceable limits. Google is not the only leading AI lab to sign such a deal—OpenAI, xAI, Nvidia, Microsoft, and Amazon have all agreed to similar contracts. Only Anthropic has refused, resulting in the Pentagon ordering the military and all defense contractors to stop using its products and labeling it a “supply chain risk,” a designation Anthropic is challenging in court.

Within Google, the deal has kicked off internal protests, with more than 600 Google employees signing an open letter opposing the deal, and several employees criticizing the agreement in the press and on social media.

In addition, the workers are asking for an independent ethics oversight body and the individual right to refuse to contribute to projects on moral grounds.

The union attempt is part of a wider campaign against Google’s military contracts that, according to the Communication Workers Union (CWU), includes in-person protests and research strikes that would include employees abstaining from work on core products such as the Gemini AI assistant.

One Google DeepMind employee with knowledge of the union bid but who asked for anonymity to speak freely about their employer told Fortune: “Hopefully this will help employees help the DeepMind and Google leadership grow a spine when it comes to standing up to what they have preached and publicly endorsed as our values and principles for the last two decades.”

Workers below VP level backed the union vote by 98%, according to the CWU, and have asked Google to recognize the CWU and Unite the Union as their official representatives. The unionization bid would cover at least 1,000 staff tied to DeepMind’s London office. Representatives for Google did not respond to Fortune’s request for comment by press time.

“By exercising their rights to collectivise, they are in a strong position to demand their employer stop circling the ethical drain of military-industrial contracts, echoing the sentiment of many working people in the UK and elsewhere,” John Chadfield, CWU national officer for tech workers, said. 

The move is an attempt to claw back some of the leverage Google employees have enjoyed in the past. In 2018, thousands of employees signed a petition and several resigned over Project Maven, eventually forcing Google to abandon the contract. 

But that leverage has since eroded, according to former and current employees who previously spoke to Fortune. Cost-cutting, AI spending, and layoffs across the tech sector have weakened bargaining power, they said.

“One of the things we can look at through unionization is restoring that leverage,” another DeepMind researcher told Fortune. “If we can manage to get a seat at the table, whether that’s in the ethics review, the AI review, deployments, or even on the Alphabet board, that’s where we could restore leverage.”

“In general, I don’t think that leverage has ever been very direct; it’s always been pointing out the problem, and making the cost to continue these controversial projects high enough that they are not worth it,” they added.

The workers’ letter gave Google management 10 working days to voluntarily recognise the CWU and Unite—or to agree to mediated negotiations—before a formal legal process is launched to compel recognition.