Hollywood stars and political leaders have angrily described the decision to pull a film about the assassination of the North Korean leader as a defeat for free speech.

US investigators have said North Korea is behind the cyber attacks on Sony Pictures which led The Interview to be shelved.

Starring Seth Rogen and James Franco, it was due to be released in America on Christmas Day and come to the UK in February.

But hackers calling themselves Guardians of Peace threatened to launch attacks like the September 11 atrocities on cinemas that showed the film.

Sony Pictures said it was pulling the movie "in light of the decision by the majority of our exhibitors not to show the film".

Some of Hollywood's best known faces took to Twitter to oppose the decision.

"Really hard to believe this is the response to a threat to freedom of expression here in America," Ben Stiller wrote.

"Terror threats shouldn't dictate free expression. That's my opinion," he added.

Rob Lowe, who stared in the West Wing, said: "Wow. Everyone caved. The hackers won. An utter and complete victory for them. Wow."

He compared the decision to pull the film to the former British prime minister Neville Chamberlain's policy of appeasement with Adolf Hitler.

He tweeted: "Saw @Sethrogen at JFK. Both of us have never seen or heard of anything like this. Hollywood has done Neville Chamberlain proud today."

Comedian Jimmy Kimmel branded the move an "un-American act of cowardice that validates terrorist actions and sets a terrifying precedent".

Oscar-wining screenwriter Aaron Sorkin, who has already attacked the media for spreading information leaked by the hackers, said: "Today the US succumbed to an unprecedented attack on our most cherished, bedrock principle of free speech."

US president Barack Obama described the cyber attack as "very serious", adding: "We'll be vigilant. If we see something that we think is serious and credible then we'll alert the public.

"But for now, my recommendation would be that people go to the movies."

Asked what David Cameron thought about Sony's decision, the Prime Minister's official spokesman said: "I have not spoken to him about it directly, but I do know that he always puts a very high importance on the principle of freedom of speech.

"Is there a very important principle around freedom of speech that we should never be shy about defending? That is absolutely a view the Prime Minister has."

Former US speaker of the house of representatives Newt Gingrich described the hack as an "act of war" by terrorists and "almost certainly the North Korean dictatorship".

He tweeted: "Sony should release The Interview online for free so North Koreans can't censor American creativity--should have Korean language version.

"No one should kid themselves. With the Sony collapse America has lost its first cyberwar. This is a very very dangerous precedent."

The attack was possibly the costliest yet for a US company, said Avivah Litan, a cyber-security analyst at research firm Gartner.

"This attack went to the heart and core of Sony's business - and succeeded," she said.

"We haven't seen any attack like this in the annals of US breach history."

News of the Sony hack first broke on November 24 after the image of a skull flashed on every Sony employee's computer screen at the same time with the warning: "This is just the beginning, we've obtained all your internal data."

Since then a series of highly damaging leaks have rocked the company, where phones and email services have been paralysed.

North Korea has denied orchestrating the cyber-attack but an unidentified spokesman for the North's powerful National Defence Commission said the attack "might be a righteous deed of the supporters and sympathisers" of the North.

The chilling effect from the hack appeared to reach other film studios, with reports that a thriller set in North Korea and starring Steve Carell under development by New Regency has been scrapped.

In a statement Sony Pictures said: "The studio, which has been shaken by hacker leaks over the past several weeks, said it respected and shared in the exhibitors' concerns.

"We are deeply saddened at this brazen effort to suppress the distribution of a movie, and in the process do damage to our company, our employees, and the American public.

"We stand by our film-makers and their right to free expression and are extremely disappointed by this outcome."

PA Media