Donald Trump's family business is launching a new Trump-branded phone service, in its latest plan to cash in on the US president's name.

The Trump Organization, which is run by his sons, said it planned to sell a gold-coloured, made-in-America smart phone for $499, along with mobile phone service for a monthly fee of $47.45 - a reference to their father serving as the country's 47th and 45th president.

The announcement was light on details, including the name of the business partner that will run the service and is licensing the name.

Ethics watchdogs said the latest venture represented another means for potential corruption and conflicts of interest.

"It's unbelievable that the Trump family has created yet another way for President Trump to personally profit while in office," said Meghan Faulkner, communications director for Citizens for Responsibility and Ethics in Washington (CREW).