A man has vowed to never go to Burger King again after staff “refused” to give tap water to a dehydrated teenage boy on one of the hottest days of the year.

Michael Casey was having coffee with his partner at the branch in Bouverie Place, Folkestone, on Sunday when he witnessed the incident.

The Dover resident was visiting the seaside town for the day and says he was left shocked at seeing the youngster denied the free drink.

Mr Casey says the Burger King staff should “hang their heads in shame” after they rejected the teenager’s request “without any real reason.”

“The boy could not have been any more polite,” he said.

“It was the afternoon on one of the hottest days of the year. The boy came in sweating and he was clearly dehydrated.”

Mr Casey told KentOnline he was left feeling “disgusted” by the behaviour of the fast-food chain’s workers.

He added: “I got the impression they found the whole situation amusing.

“I felt they were mocking the boy. I definitely will not be going back.”

After sympathising with the teenager, Mr Casey proceeded to buy him a drink of his choice.

“I felt sorry for the lad. I told him he could buy any drink he wanted,” he said.

“Even then, he still told me he was fine with tap water and could not have been more thankful to me.”

The 66-year-old explained he did not care about the cost and spent more than £2 on some water for the boy.

Mr Casey posted about the incident on Facebook, attracting more than 120 comments – with most supporting him and blasting Burger King.

Heather Mitchell said: “Shocking in this heat. Shame on the staff.”

Christine Warne added: “You are entitled to ask for water when the temperature is that high! Who would refuse anyone a drink of water?”

A spokesperson for Burger King told KentOnline drinking water is always free and readily given to customers.

“Providing a superior guest experience is a top priority at Burger King restaurants globally,” they said.

“We are liaising with the restaurant around this matter and would like to reiterate and reassure customers that where available, drinking water is always free and given readily to guests.”

All licensed premises are required by law to provide "free potable water" to their customers upon request – but only if authorised to serve alcohol.

These businesses can charge people for the use of a glass – or their service – when serving the "free" tap water.