Just Stop Oil is whining that the German protester, who sparked a 40-hour gridlock when he climbed Dartford Crossing bridge, will be kicked out of the UK when freed from jail.
Marcus Decker, who has leave to remain in the UK, said he had been served with a stage one deportation order.
The 34-year-old and fellow campaigner Morgan Trowland, 40, used ropes and other equipment to scale the 450ft high bridge at the Dartford Crossing last October.
The stunt by Just Stop Oil caused 40 hours of gridlock as police were forced to shut the crossing to traffic amid safety concerns for him and Trowland.
They were given sentences of two years, seven months, and three years for the stunt.
The group are staging another public march today to ‘demand the Home Office to end deportations of peaceful demonstrators’.
It started midday at Parliament Square and are making their way to Home Office, with speakers including Marcus, via telephone from prison, and his partner Holly Cullen-Davis.
A petition calling to secure Marcus’ right to remain in the UK has over 79,000 signatures.
Just Stop Oil spokesperson, Indigo Rumblelow said: ‘We will be sending a clear message to the Home Secretary that the cowardly ”double punishment” of peaceful people in civil resistance to stop government criminality and protecting the lives of their families will not go unchallenged.
‘We’re demanding that Marcus stays in the UK and is not deported at the end of his sentence so that he can remain with his family, friends, and stepchildren.’