A tweet in which Donald Trump extolled the virtues of his golf course near Aberdeen was “shameless, corrupt and repugnant”, a leading US ethics expert said.

The president sent the tweet in the early hours of Saturday. He later went on to deliver a rambling, controversial and sometimes obscene speech at the Conservative Political Action Conference, or CPAC, near Washington.

“Very proud of perhaps the greatest golf course anywhere in the world,” Trump wrote, embedding a Trump Organization tweet in praise of Trump International Scotland, the Aberdeenshire course he opened in 2012. “Also, furthers UK relationship!”

In response Walter Shaub, a former head of the independent US Office of Government Ethics, wrote: “This is Trump’s most explicit commingling of personal interests and public office to date. This is the tone from the top that leads his appointees to violate ethics rules. This is shameless, corrupt and repugnant presidential profiteering. This is an invitation to graft.”

Shaub, who was appointed to the ethics role under Barack Obama before resigning under Trump, is a regular and fierce critic of the president.

Trump nominally handed control of his business to his sons when he entered the White House. Nonetheless, he has been widely accused of violating the clauses of the US constitution designed to stop presidents profiting from the office.

On Saturday, the watchdog Citizens for Ethics, which Shaub advises and which is suing Trump over such issues, tweeted: “There it is. The president is using an official statement as an ad for his business and making sure everyone knows he ties his business to US relationships with foreign countries.”

Trump owns two courses in Scotland, the other being Turnberry in Ayrshire, which he bought in 2014 and at which he played during a visit to Britain last summer that prompted widespread protests, not least across Scotland.

The investments have been expensive and controversial. Recently, a proposal to build 550 luxury villas at the Aberdeenshire course was delayed, having been the subject of a record number of complaints.