Sir Lindsay Hoyle has written to MPs warning them about Russian-linked attempts to target them on WhatsApp and other messaging apps.
The letter, seen by the Press Association, warns parliamentarians of a rising number of phishing attempts linked to Russian actors.
The attacks, where a hostile actor attempts to trick people into sharing sensitive information or compromising their accounts to access it, have been growing on messaging platforms like Signal and WhatsApp which are widely used by MPs and UK officials, the letter says.
The National Cyber Security Centre (NCSC) urged MPs to take further steps to bolster their security in light of the rise in phishing threats, and advised MPs to not use informal messaging apps for parliamentary work.
A Government spokesperson said: “Spear-phishing is a common but all-too-effective tactic used by threat actors attempting to gain access to information, online accounts and devices.
“The National Cyber Security Centre is working with partners in Government and UK Parliament in response to recent targeting against commercial messaging apps including Signal and WhatsApp.
“We strongly encourage individuals at high risk of being targeted to follow the NCSC’s guidance and to sign up for our cyber defence services to help bolster their protection.”
The warning comes after parliamentarians were last month warned of attempts by the Chinese intelligence service to recruit them in order to access sensitive information.
Security minister Dan Jarvis at the time told the House of Commons that China was attempting to “recruit and cultivate” individuals with access to sensitive information about Parliament and the UK Government, often masked through cover companies and head-hunters.