Batman star Christian Bale's arrest over an alleged assault on his mother and sister may have been linked to grief over the loss of his friend Heath Ledger.

Sources told Britain's Daily Mail that Bale had been deeply affected by the Australian actor's death from an accidental overdose, and that Ledger's loss had affected Bale's ability to communicate with those around him.

Bale, who plays Batman in The Dark Knight, was arrested and bailed over the alleged assault on Tuesday, after he spent four hours at a London police station.

Bale lost his temper in a London hotel room after his mother allegedly insulted his wife, the Mail report said.

Bale and Ledger, who plays a maniacal Joker in the latest Batman flick, became mates when they both played Bob Dylan in the 2007 movie I'm Not There.

An unnamed friend told the Mail: "Christian pretends he's calm and collected but you really started to see the cracks in his facade in January, right after Heath Ledger had died.

"Christian was in the middle of a very brief break from work when he heard the news, and it was massive blow to him.

"They had become very close during the making of The Dark Knight and Christian went into virtual hiding for the six weeks after Heath was found dead.

"He wasn't returning phone calls and he wasn't a happy man.

"It's foolish to think that he's been able to completely shake off that grief just as Heath and his work is finally being seen by audiences.

"He expected to share this moment with his friend, and now he can't."

A source close to the actor said Bale was confident he had done nothing wrong, and blamed his mother for the drama.

"Christian was stressed, but he didn't lay a finger on anyone. Instead, he flew off the handle and cussed his mother. He just got very loud because his mother was saying some very outrageous things about him, his wife," the source said.

"Christian's attitude is that this was his mother's fault because she became very provocative in an argument they were having.

"Things got out of control and he says now he wishes he just left the room."

The source said his mother's hurtful comments came at a time when Bale's marriage to his former-model wife, Sandra 'Sibi' Blazic, was enduring difficulties.

"He has stresses in his marriage. He can have a terrible temper. Instead of lashing out at his wife, he sometimes lashes out at people around him."

The source agreed the death of Ledger - whose performance as The Joker has eclipsed all others in the film, and drawn talk of a posthumous Oscar nomination - had deeply affected Bale.

"Without Ledger around he's found it more and more difficult to communicate with those around him, especially his family."

Asked on Tuesday whether Bale had been arrested, a London police spokesman did not refer to him by name but said: "A 34-year-old man attended a central London police station this morning by appointment and was arrested in connection with an allegation of assault."

British police do not name suspects before they are formally charged.

The force later said in a statement that the man had been released on bail pending further inquiries and told to return in September. It did not specify the date.

Bale's sister Sharon told reporters "it's a family matter" from her home in Corfe Mullen, southwest of London.

A man who answered the door at the home of his mother, Jenny Bale, in nearby Bournemouth said she did not want to comment.