Singapore police arrested a British author on Sunday, a day after he launched a book alleging double standards in the city-state's use of the death penalty.

Alan Shadrake, who wrote the book Once a Jolly Hangman: Singapore Justice on the Dock, was detained on charges including criminal defamation and contempt of court, police said in a statement.

"Police confirm that they have arrested British national Alan Shadrake. He is being investigated for alleged offences of criminal defamation and other offences," it said.

"Alan Shadrake has also been served with an application by the Attorney-General for an order of committal for contempt of court," the statement added.

It said that the arrest was made "pursuant to a police report that was lodged" by regulator Media Development Authority.