The US is attempting to secure immunity from investigation for online security breaches by major US companies under negotiations between Washington and Brussels, according to leaked documents seen by the Guardian.

Such a deal would prevent US companies that were operating inside the EU from being prosecuted by regulators or law officers for data breaches or claims of negligence in the host country, forcing European governments to pursue cases in the US courts.

Public service unions said the Trade in Services Agreement (Tisa) talks in Geneva revealed how the US planned to protect homegrown businesses from regulations that might hinder their expansion into sensitive areas such as government data handling and healthcare.

Rosa Pavanelli, general secretary of Public Services International (PSI), which represents 650 unions in 150 countries, said the leaked documents, obtained by the Associated Whistleblowing Press, confirmed her fears that “Tisa is being used to further the interests of some of the largest corporations on earth”.

She said: “It is now clear the US wants to use its trade agenda to remove restrictions to data being held or processed in other countries.”

Viviane Reding, a former EU commissioner and Christian Democrat MEP, said the leaks showed the US was using Tisa to unravel EU data protections through the back door. She tweeted that she would oppose “any provision undermining right to privacy”.

The Tisa talks involve 23 members of the World Trade Organisation (WTO), including the EU and are run in parallel with the TTIP trade talks between the EU and US that focus on lowering tariffs to promote free trade. Such is the scope of the Tisa deal, it would set the legal and regulatory framework covering 70% of world trade in services.

One of the most enthusiastic supporters of the Tisa is the Coalition of Services Industries (CSI), a lobby group for companies such as Google, IBM, AT&T and Mastercard.

The EU commission said a deal is needed to make it easier for EU firms to export services to other countries and help secure growth and jobs. It added: “Making it possible for firms from outside Europe to offer their services in the EU will increase choice and lower prices for businesses and consumers alike.”

Details of its own position are published on the commission’s website and will need to be ratified by the EU parliament. Reding is likely to play a key role in any ratification process since assuming the role of the European parliament trade committee’s rapporteur on Tisa.

Officials in Brussels have stressed EU governments were against any deal that allowed foreign firms to escape local data protection laws. Germany, in particular, is concerned about data security following the revelations that the US National Security Agency tapped Angela Merkel’s phone.

Commission president Jean-Claude Juncker has previously said data protection would not be “sacrificed on the altar of free trade”.

However, little is known about the progress being made towards a Tisa framework since negotiators agreed to keep documents related to the talks under wraps for at least five years. They have also refused to divulge proposals put forward by participants that wish to keep them out of the public domain.

In a statement on its website, the EU said: “Tisa aims at opening up markets and improving rules in areas such as licensing, financial services, telecoms, e-commerce, maritime transport and professionals moving abroad temporarily to provide services.”

Critics of the talks argue the US is attempting to strong-arm the EU into conceding that US firms should remain under the jurisdiction of US laws and regulators even when they win contracts to provide government contracts.

Rosa Pavanelli, of PSI, which represents 650 unions in 150 countries, said: “The leaked documents confirm our worse fears that Tisa is being used to further the interests of some of the largest corporations on earth.

“It is now clear the US wants to use its trade agenda to remove restrictions to data being held or processed in other countries.

“The removal of restrictions on data movement in secret negotiations places the negotiating governments well beyond the expectations their citizens have of trade deals.”

PSI fears that provisions outlined in the leaked documents potentially circumvent privacy laws.

“Negotiation of unrestricted data movement, internet neutrality and how electronic signatures can be used strike to the heart of individuals’ rights. Governments must come clean about what they are negotiating in these secret trade deals,” Pavanelli said.

Daniel Bertossa, director of policy at PSI, said the US negotiators wanted to prevent signatory countries from preferring locally produced e-content to the advantage of Hollywood and the US entertainment industry.

He said: “Unless preference can be given to local suppliers, local content will simply not be produced in many countries. Small local producers just won’t survive against large multinationals”.

The EU said Tisa would not force governments to privatise publicly-funded health and social services, education water collection, film, TV and other audiovisual services. It denied the talks were secret, saying the council of ministers and the EU parliament would be kept informed. “We also meet frequently with representatives of civil society,” it said on its website.