Bale, 34, attended a police station after it was reported his mother and sister had reported him to police.
The alleged incident was believed to have taken place on Sunday night at Park Lane's Dorchester Hotel where Bale is staying.
His mother Jenny, 61, and sister Sharon, 40, are said to have gone to a police station in Hampshire to make the allegation, which was subsequently referred to the Metropolitan Police.
A Met Police spokesman said: "A 34-year-old man attended a London Police Station on Tuesday by appointment and was arrested in connection with an allegation of assault.
"He currently remains in custody."
Despite the alleged incident and report, Bale was allowed to attend the first European screening of the new Batman blockbuster The Dark Knight in London's West End on Monday night uninterrupted.
Bale was joined on the red carpet by Maggie Gyllenhaal, who plays love interest Rachel Dawes, and Sir Michael Caine who plays Bruce Wayne's faithful butler and father figure Alfred.
The film took a record $158.3 million in its opening weekend at the US box office overtaking Spiderman 3, which took $151.1 million.
Interest in the film has increased because of the death of Heath Ledger.
His performance as Batman's arch nemesis The Joker, has been widely tipped by critics, as well as Caine, to receive a posthumous Oscar.
http://www.telegraph.co.uk/news/new...an-Bale-arrested-over-assault-allegation.html