Pheu Thai's de facto leader, Thaksin Shinawatra, has come under fire over racist remarks he allegedly made during a campaign rally in Chiang Rai.

During the rally Thaksin delivered a speech to encourage more Thais to find opportunities in the entertainment industry.

However, he made disparaging comments about models from Africa in his speech, which were widely seen as racist.

"African people, who have black skin and flat noses that make it difficult to breathe, are hired for millions of baht to be models. Thai people look much better. There's no need for [our people to get] nose, jaw or breast augmentation.

"It's time to encourage more Thais, including those from ethnic groups like the Karen, who possess natural beauty, to become international models," he said.

Senator Angkhana Neelapaijit on Monday demanded that Thaksin publicly apologise for the comments.

Ms Angkhana, a former member of the National Human Rights Commission, also urged Prime Minister Paetongtarn Shinawatra, Thaksin's daughter, to take the matter seriously.