Britain is fighting Russia in the “grey space” between normal diplomatic relations and open warfare, the former cabinet secretary has said.
Lord Mark Sedwill, who left his post as the most senior civil servant last month, said the UK was trying to “impose a price greater than one [Russia] might have expected” in response to the Salisbury attack and other aggressions.
“Russia is operating in what the aficionados call grey space, that gap between normal state relations and armed conflict, with cyberattacks, information warfare and disruption campaigns,” he told Times Radio.
“It is important that we are capable of manoeuvring in the grey space and doing so effectively. We can’t leave the initiative to our adversaries.
“There are vulnerabilities that we can exploit too. We just don’t always talk about them.”
Lord Sedwill, who was also the national security adviser until he stepped down in September, said Britain was deploying its recently declared offensive cyber capability against Russian assets.
He said the measures included action against some of the “illicit” money flowing out of Russia, and covert operations.
The 2018 Salisbury attack, where Russian agents attempted to assassinate Sergei Skripal with novichok, triggered a wave of international diplomatic expulsions.
Lord Sedwill said it was a “visible way” of retaliating against the first use of chemical weapons against a European country in a century, adding: “We expelled the entire Russian intelligence network in the UK.
“But we also took a series of other discreet measures, including measures tackling some of the illicit money that flows out of Russia, and covert measures, which obviously I can’t talk about, as well.”
Lord Sedwill announced his departure as cabinet secretary and national security adviser in June amid reported tensions with the prime minister and Dominic Cummings, and allegations that he had been unfairly smeared.
He has since been granted a life peerage and sits as a crossbench peer in the House of Lords.
A report on Russia published by parliament’s Intelligence and Security Committee in July said the government had “badly underestimated the Russian threat and the response it required”.
It said Russia considers the UK one of its top western intelligence targets, and uses malicious cyberactivity, disinformation, and attacks on government departments and critical national infrastructure.
The report said security policy had not been changed when the UK was opened up to Russian investment, and that the UK “now faces a threat from Russia within its own borders”.
“What appears to have been a somewhat laissez-faire policy approach is less easy to forgive than the response of the busy [intelligence] agencies,” the committee added.
“We welcome the fact that this has now been recognised and appears to be changing.”
Additional reporting by PA