Media playback is unsupported on your device Media caption Gambler Mark Johnston: "Any other casino would have stopped me"

A US businessman who lost $500,000 (£298,000) at a Las Vegas casino says he should not have to pay - because he was too drunk.

Californian Mark Johnston has sued the Downtown Grand for serving him drinks and lending him money while he says he was clearly intoxicated.

The 52-year-old arrived at the casino on 30 January and played at the tables for 17 hours.

Under Nevada law, patrons who are visibly drunk are not meant to gamble.

The casino, which has not commented, reportedly intends to legally pursue Mr Johnston for the debt.

'Blackout intoxicated'

A car dealership and real estate businessman, he lost the money at the casino on Super Bowl weekend.

Mr Johnston says the Downtown Grand served him 20 alcoholic beverages during his gambling session, on top of about 10 drinks he had consumed before even arriving at the casino.

"Look, I had some drinks at the airport," he told CNN. "I had a drink on the plane. You know, at some point that's my responsibility, OK.

"But the unfortunate part about it for them [the casino] is that they have a more, bigger responsibility than I do."

He added: "Just picture a drunk walking down the street and somebody goes up and just pickpockets him. That's how I characterise it."

His lawyer, Sean Lyttle, told the Associated Press news agency it was an "extraordinary case".

"Someone was blackout intoxicated where they couldn't read their cards, and yet a casino continued to serve them drinks and issue them more markers," he said.

Mr Lyttle said his client had put a stop-payment order on the markers issued by the Downtown Grand, and was also seeking damages from the casino for sullying his name.

The Nevada gaming control board is said to be investigating the matter.