Denis Sergeev is thought to have been the senior member of the Russian military intelligence team.
The government is likely to help big gas providers forced to take customers from failed firms.
The former Russian spy, who became a British citizen, was poisoned in London with polonium in 2006.
Insulate Britain protesters blocked traffic on both carriageways of the motorway in Surrey earlier.
Defence Secretary Ben Wallace has launched an investigation, while the MoD has apologised for the breach.