'I understand staff morale has suffered,' said Mr Chu Pui Hing, director of broadcasting at Radio Television Hong Kong (RTHK), who is married with two sons.

He told reporters he had originally planned to resign in 10 months' time but decided to quit early after the scandal hit the headlines in local newspapers in the past few days.

Mr Chu, 59, has worked at RTHK for more than 30 years.

His pay grade is D5, according to RTHK spokesman Kirindi Chan. That makes his salary HK$154,150 (S$30,000) a month, the civil service website shows.

He was spotted at about 10pm on Thursday emerging from a building in Causeway Bay after a private dinner with some friends.

He was holding hands with a woman whom local papers called 'Coco'.

Reporters from several Chinese newspapers had gone to the building to interview singer Kenny Bee and spotted Mr Chu by chance.

Mr Chu hid behind the woman when he was discovered by photographers, reported The Standard newspaper.

The couple later split up when reporters and photographers continued to follow them.

He ran into a Japanese karaoke venue, leaving the woman alone in the street.

Another man later appeared and took the woman into a nearby Chinese restaurant, according to the South China Morning Post.

The woman was later identified as a 23-year-old from Sichuan province who is reported to be working in several karaoke bars.

She arrived in Hong Kong two years ago on a two-way permit, which allows mainlanders to visit relatives, according to Apple Daily.

Mr Chu denied newspapers reports that the woman was paid to keep him company.

'That was a private gathering with a few friends, who have nothing to do with RTHK affairs, and there was no one taking any benefits,' he said.

'My wife and family have accepted my explanation and they support me.

'I apologised for the embarrassment. I apologised for my acting out of character.'

BLOOMBERG