US Supreme Court Justice Clarence Thomas has acknowledged he took three trips aboard a Republican donor’s plane last year, as an ethics row grips the top court.

The conservative judge said failing to previously report receiving such hospitality had been “inadvertent”.

Supreme Court judges are required to file annual financial disclosure forms.

Justice Thomas was the last to do so, but is not the only one facing potential conflicts of interest.

Critics are pushing to review and reform ethics standards for the nine justices who receive lifetime appointments to the nation’s highest court.

It follows a series of US media reports that revealed Mr Thomas, 75, had failed to disclose several expensive gifts from Harlan Crow, a wealthy real estate developer and conservative benefactor.