Ministers have been given new guidance on using WhatsApp and other private messaging apps for government business.
It replaces previous guidelines from 2013, before WhatsApp was widely used, on the use of private email.
The new guidance states that ministers and officials should use private messaging apps "with care" and never for information classified as "secret".
It follows concerns over the use of WhatsApp to discuss key decisions during the Covid
Last year, a report by the Information Commissioner's Office (ICO) found a lack of clear controls and a rapid increase in the use of messaging apps like WhatsApp could lead to important information about the government's response to the pandemic being lost or insecurely handled.
The watchdog highlighted risks to transparency and accountability and called for a review into the use of private correspondence channels in government.
The issue was thrown into the spotlight again earlier this month when the Daily Telegraph newspaper revealed it had obtained more than 100,000 messages sent between then-Health Secretary Matt Hancock and other ministers and officials at the height of the pandemic.
The new guidance, issued by the Cabinet Office, applies to ministers, special advisers, officials, contractors and independent experts advising ministers.
It advises that departments should reduce the need for non-corporate communication channels, including WhatsApp, Signal, private email, text messages and private messaging on social media platforms like Facebook
, "as far as reasonably practicable".
In general, it says government systems should be used for government business and care should be taken over recordkeeping responsibilities.
Under the guidance, information classified as "secret" or "top secret" - the highest level of security classification - must not be shared on private messaging channels.
It also outlines how significant government information should be captured into government systems to help accountability.
In particular, it highlights how any use of "disappearing message" functions must not impact on recordkeeping or transparency, although it says such tools "have a role in limiting the build up of messages on devices".
It comes after reports suggested some cabinet ministers were using the function on Whatsapp, which allows users to set messages to automatically disappear after a certain timeframe.
There have also been concerns that ministers could have deleted messages with key information about the government's Covid
response, ahead of the independent public inquiry.
Lord Bethell, who was a health minister during the pandemic, admitted he had "clumsily deleted" some WhatsApp messages because "there simply wasn't enough space on my phone".
The ICO said there was "a clear improvement" in the new guidance and that it addressed some of the concerns raised in its 2022 report.
The watchdog's director of freedom of information and transparency, Warren Seddon, added: "However, we remain disappointed that the more strategic review we recommended, which asked government to review the risks and opportunities in more detail, has not yet been conducted."