The Green Party is calling on the shale gas company, Cuadrilla, to answer allegations of violence by security guards and staff against protesters at its site near Blackpool.

Party co-leader, Jonathan Bartley, hand-delivered a letter to Cuadrilla’s chief executive today expressing “grave concern” about two recent incidents.

Last week security staff allegedly punched an activist and were photographed holding him by the throat. On Monday a protester was hit by a van leaving the site.