Matthew Weaver and agencies

guardian.co.uk, Monday 3 January 2011 11.25 GMT

The actor Pete Postlethwaite has died at the age of 64. Friends said he passed away peacefully in hospital in Shropshire yesterday having suffered from cancer for some time.

Postlethwaite was once described by the film director Steven Spielberg as “probably the best actor in the world today”.

He worked with Spielberg on two films in 1997 – the fantasy adventure film The Lost World: Jurrassic Park, and Amistad, about a slave mutiny on a ship.

The craggy-featured actor received an Oscar nomination for his performance as Guiseppe Conlon in the 1993 film In The Name Of The Father, about the wrongful convictions of the Guildford Four.

His notable films included the 1996 film Brassed Off, in which he played the leader of colliery band in a Yorkshire community devastated by mine closures. The film was a favourite of the former deputy prime minister John Prescott, and became the inspiration for a coalfield regeneration programme.

Postlethwaite also played the menacing criminal mastermind Kobayashi in the 1995 hit film The Usual Suspects.

In recent years Postlethwaite became known as much for his political activism as his acting. He was the front man in the climate change film The Age of Stupid, arriving at the 2009 London premiere on a bicycle.

After the film’s release he threatened to hand back the OBE he was awarded in 2004 in protest at the government’s controversial decision to give the go-ahead for Kingsnorth coal-fired power station in Kent.

He also adapted his home to become environmentally responsible, installing a wind turbine and other features.

In 2003 he marched against the war in Iraq and was a vocal supporter of the Make Poverty History campaign.

Born in Warrington, Postlethwaite had originally planned to be a priest. He became a teacher but eventually took to the stage, beginning his career at the Everyman theatre in Liverpool. In 2008 he returned to the Everyman to play the lead in King Lear, a role he had always wanted to play. The performance was one of the highlights of Liverpool’s year as the European Capital of Culture.

He is survived by his wife, Jacqui, his son, Will, and daughter, Lily.