“Many people, not just in politics, use disappearing messages,” he added.
The disappearing message tool allows WhatsApp users to set a time limit of 24 hours, seven days or 90 days, after which their texts are deleted.
Guidance for ministers says disappearing messages are permitted as long as they don’t affect record keeping or transparency.
However, a review is under way into the use of WhatsApp and the prime minister’s official spokesman admitted there were “lessons to be learnt”.
The spokesperson noted that the papers did contain “multiple” documents from the prime minister’s private office, which he said was “the standard and established route for communicating prime ministerial decisions and handling communications”.
Conservative shadow minister Alex Burghart said: “Government guidance is clear: significant information and decisions must be properly recorded and preserved.
“But Keir Starmer’s messages to Peter Mandelson have been disappeared or destroyed.”
On Monday, chair of the Intelligence and Security Committee, Lord Beamish called on senior officials and ministers to stop using WhatsApp to conduct government business.
The Labour peer said there were concerns about security as well as the lack of an audit trail for decision-making.
“These are all issues that the last committee raised with both the Johnson and Sunak Governments. That culture is continuing; it cannot be allowed to continue.”
Other cabinet ministers including the Deputy Prime Minister David Lammy and the Chancellor Rachel Reeves also use disappearing messages.