Shadow chancellor John McDonnell is under fire after employing a former Momentum and Green Party staffer to work in his office.
Joe Ryle helped organise for activist group Momentum in London, where some MPs fear it is behind attempts to deselect them.
He also played an active role in aviation campaign group Plane Stupid, with whom he was arrested after a protest at Stansted Airport.
A Labour MP told the Standard: "It has been widely reported that Momentum is being used as a vehicle to mount deselection campaigns against moderate Labour MPs.
"Is it really appropriate for a former Momentum officer to be employed in the office of the shadow chancellor?
"I can only assume the Green Party must have given him a very good reference."
Within the last year, Mr McDonnell’s new employee has worked as a press officer to Green MEP Keith Taylor.
In 2008 Mr Ryle was among a group of climate-change protesters who brought Stansted to a standstill.
He and 21 other Plane Stupid members admitted aggravated trespass.
Neither he nor the shadow chancellor’s office would comment today.
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