Campaigning legal organisation, Good Law Project, has launched judicial review proceedings, arguing the use of unofficial communications systems is in breach of government obligations to preserve records of decision-making.
They also claim the use of private email and messaging services undermine the government’s ability to comply with freedom of information requests.
The GLP states that existing Cabinet Office policy regarding the use of private emails gives no guidance on when or why they should be used by ministers or officials, and is therefore “not fit for purpose.”
While it not against the rules for ministers to use private email, Cabinet Office guidelines say "substantive discussions” and formal decisions should be accessible, and the government has said official business is conducted in line with guidance.
However the GLP’s pre-action notice refers to WhatsApp messages recently published by the Prime Minister's former adviser Dominic Cummings, which appear to show government business being discussed, and refers to reports in the Sunday Times that former health secretary Matt Hancock used a private Gmail address for government business.
Health minister Lord Bethell, who is named in the action, has also said that while some third parties "in their enthusiasm" often contact ministers via their personal email accounts, "that's not the same as using a personal email for formal departmental decision-making.
"I am absolutely rigorous in ensuring that government business is conducted through the correct formal channels."
The UK's data watchdog is already looking into the use of private email accounts at the department for health with Information commissioner Elizabeth Denham expressing concern it could lead to a "loss of transparency" with information in private email accounts or messaging services being “forgotten, overlooked, auto-deleted or otherwise not available when a freedom of information request is later made.”
Labour has also demanded a "full scale investigation" into whether private emails had been used to discuss government business, particularly Covid contracts.
The GLP, which campaigns for transparency, has previously raised concerns about the awarding of government contracts during the pandemic.
Gemma Abbott, the organisation’s legal director, said: “Government’s current policy on the use of private email is not fit for purpose and it seems ministers aren’t taking much notice of it in any event.
"Perhaps most concerning is that it appears some in government think the use of private communication channels is a means of avoiding proper scrutiny.
“We don’t just think the current approach is wrong, we think it’s unlawful.
"If successful, this legal action could close this accountability gap, paving the way for a robust, lawful policy on the use of private email and WhatsApp.”
The government has 14 days to respond to the pre-action notice before a court decides if a judicial review goes ahead.
A government spokesperson said: "There are appropriate arrangements in place for the management of electronic communications, including instant messages and emails.
"Ministers and officials are aware of the guidance around personal email usage, and government business is conducted in line with that guidance."