Singapore is due to hang Tangaraju Suppiah, 46, on Wednesday for abetting the trafficking in 2013 of more than 1 kg of cannabis, double the threshold for awarding the death penalty in the city-state, which is known for its tough laws on narcotics.
Branson, a well known opponent of the death penalty, in a blog post said the verdict against Tangaraju did not meet standards for criminal conviction, and that "Singapore may be about to kill an innocent man", as he was not near the drugs when he was arrested.
Singapore's home ministry in a rebuttal said its courts spent more than three years examining the case and Branson's claim was "patently untrue".
"It is regrettable that Mr. Branson, in wanting to argue his case, should resort to purporting to know more about the case than Singapore's courts," it said.
Singapore executed 11 people last year and says the death penalty is a deterrent against drugs that most of its people support.
Many of Singapore's neighbours have no death penalty or have observed moratoria on executions, including Malaysia, which earlier this month passed sweeping legal reforms to end mandatory capital punishment.
Tangaraju's family have sent letters to Singapore's president seeking clemency, while the local missions of the European Union and its member states have jointly called for him to be given a non-capital sentence.
Singapore and Branson have previously locked horns over the death penalty and the Briton criticised authorities last year for hanging a Malaysian man convicted of trafficking heroin, who activists said was intellectually impaired. Branson declined Singapore's invitation for him to join a debate on the issue.
(Reporting by Chen Lin; Editing by Martin Petty)
By Chen Lin
