Brad Pitt says gay marriage is 'inevitable' and publicly backed Barack Obama's campaign to be re-elected President of the United States.

'I am an Obama supporter and I’m backing his election campaign,' Pitt told The Telegraph at a screening of his forthcoming film Killing Them Softly.

'Gay marriage is inevitable. The next generation, they get it. It is just a matter of time before it becomes a reality.'

The Hollywood superstar's remarks come after his mother Jane Pitt shocked the gay rights advocate’s fans when she decided to write a letter to a Missouri-based newspaper slamming marriage equality and urging people to back Republican nominee Mitt Romney.

Pitt is a well-known fighter for LGBT rights, contributing $100,000 to the campaign to defeat California’s Proposition 8 in 2008.

He played gay United States District Chief Judge Vaughn R. Walker in Dustin Lance Black’s play ‘8’, who came out after ruling Prop 8 was unconstitutional.

Some have argued Pitt also played bisexual or gay in the 1994 movie Interview With A Vampire, in which he has an ‘intense’ relationship with Tom Cruise’s character Lestat.