Government plans to revamp Britain’s official secrets legislation risk making it easier to prosecute journalists reporting on national security issues and sources who work with them, the National Union of Journalists has said.

This week Boris Johnson’s new government announced plans to introduce legislation to give MI5, MI6 and GCHQ “the tools they need to disrupt hostile state activity”.

The NUJ said it was concerned that the Conservatives wanted “to regurgitate flawed proposals” drawn up by the Law Commission in 2017 as a starting point for changes to laws dating back to 1911 and 1989.

An NUJ spokesperson said: “The union expressed opposition at the time because the proposals included making it easier to prosecute journalists and increased the likelihood of conviction.”

At the time, the Law Commission argued that offences relating to official secrets “should be capable of being committed by someone who not only communicates information, but also by someone who obtains or gathers it” – a definition that would encompass any reporter.

Other proposals made by the commission included broadening the definition of official secrets to “information that affects the economic wellbeing of the United Kingdom in so far as it relates to national security”.

Journalists have periodically been prosecuted under existing rules. In August 2018, two reporters, Trevor Birney and Barry McCaffrey, who were working in Northern Ireland, were arrested and threatened with prosecution under the Official Secrets Act. The two men were making a documentary investigating the Royal Ulster Constabulary’s handling of the 1994 Loughinisland massacre by UVF loyalist paramilitaries, in which six Catholic men died. The case was finally dropped in June this year.

The human rights lawyer Clive Stafford Smith said the detail of any new espionage legislation would be critical, and he warned: “Too often the state tries to use official secrecy as a way of hiding things that are embarrassing, such as the involvement of the British state in torture or rendition.”

A film, Official Secrets, depicts the story of Katharine Gun, a translator working for GCHQ who in 2003 leaked to the Observer a request to eavesdrop on non-permanent members of the UN security council to get a better understanding of whether they would support a resolution authorising the invasion of Iraq. Gun was prosecuted under the Official Secrets Act but the case was dropped a year later.

The plans for new espionage legislation were contained in two pages of notes included as part of the briefing on the legislative agenda set out in the Queen’s speech. The document noted that the Law Commission had been asked by the government to review the Official Secrets Acts, the most important of which are the first, from 1911, and the most recent, dated 1989.

The commission’s initial proposals were put out in 2017 but the exercise ground to a halt as the Brexit crisis prevented other legislation from being introduced. The body, which is independent of government, said it would review responses from the likes of the NUJ and publish its final recommendations in the first half of 2020.