Thailand’s King Vajiralongkorn has denounced as “inappropriate” his sister’s unprecedented bid to run for prime minister in March’s election.

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.

Analysts say the king’s intervention is likely to lead to the election commission disqualifying her from the 24 March election.

The vote is being closely watched as the first chance for Thailand to return to democracy after five years under military rule.

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In a palace statement broadcast on all Thai TV networks, the king said: “Even though she has relinquished her royal titles in writing, she maintained her status and carried herself as a member of the Chakri dynasty.