An influential Thai politician was filmed slapping a female reporter after she asked him a question, sparking a formal investigation into his conduct.

Prawit Wongsuwon, 79, a veteran MP and former army chief, struck the woman several times as she was surrounded by other journalists last week.

“This behaviour is physical harassment,” said Tewarit Maneechai, a senator, who said he had requested a parliamentary investigation into Mr Prawit’s conduct.

“It is also disrespectful to a journalist who was doing her work,” he added.

The incident happened on Aug 16 moments after the Pheu Thai Party’s Paetongtarn Shinawatra won a vote in parliament to become prime minister.

Ms Paetongtarn, 37, will be Thailand’s youngest ever premier and the third from the billionaire Shinawatra family, with whom Mr Prawit has a bitter history.

Mr Prawit, who leads the Palang Pracharat Party and did not attend the vote, was asked his thoughts on the victory by the female TV journalist.

He barked back: “What are you asking? What are you asking?” and then hit her several times on the head, TV footage showed.

‘He was teasing her’

Piya Tavichai, a spokesman for the Palang Pracharat, said Mr Prawit knew the reporter well and has apologised, adding that he will clarify the facts in any parliamentary process.

“He was teasing her as someone who he is close to,” Mr Piya added. “Because he was a soldier, the teasing could appear to be violent but those close to him know that he teases like this all the time.”

The incident sparked widespread condemnation from Thailand’s media community. ThaiPBS, the country’s public broadcaster, asked Mr Prawit to take responsibility for his actions.

Mr Prawit is a notorious political dealmaker and a central figure in Thailand’s two decades of political strife. He was deputy prime minister for nine years after a 2014 coup he took part in.

Senator Tewarit said he had requested an ethics probe into Mr Prawit through the Senate to be conveyed to the lower house of parliament, which will have 30 days to respond.

He said he was unsure what penalty Mr Prawit would face if found guilty.