More than 30 public figures including Emma Thompson, Imelda Staunton and Greta Thunberg have written to Shell criticising its “callous and vindictive” lawsuit against Greenpeace after activists occupied a moving oil platform last year.

In one of the biggest legal threats in the environmental charity’s 50-year history, Shell is suing it for $1m (£790,000) in damages, with costs that could run into the millions.

The move follows a protest in January last year in which four Greenpeace activists boarded a platform north of the Canary Islands that was being transported to the Shetland Islands, holding signs stating: “Stop drilling – start paying.”

Monday’s letter , signed by dozens of prominent musicians, activists, and lawyers as well as more than 100,000 members of the public, calls on Shell to respect the right to protest.