Thailand’s King Vajiralongkorn has denounced as “inappropriate” his sister’s unprecedented bid to run for prime minister.
In a palace statement, he said such an act would “defy the nation’s culture”.
Princess Ubolratana Mahidol, 67, has been nominated as a candidate for a party allied to divisive former PM Thaksin Shinawatra.
Such a move would break with the tradition of the Thai royal family publicly staying out of politics.
Thailand’s election is due to take place on 24 March.
It is being closely watched as the first chance for Thailand to return to democracy after five years under military rule.
In a palace statement read out on all Thai TV networks, the king said: “Involvement of a high-ranking member of the royal family in politics, in whatever way, is considered an act that defies the nation’s traditions, customs, and culture, and therefore is considered extremely inappropriate.”
Hours earlier, Princess Ubolratana defended her decision to run for office.
In an Instagram post, she reiterated that she had relinquished all her royal titles and now lived as a commoner.
She said she wanted to exercise her rights as an ordinary citizen by offering her candidacy for prime minister. She said she would work with all sincerity and determination for the prosperity of all Thais.