Seven children were taken to hospital for heatstroke after spending hours in coaches stuck at a standstill on the M25 on one of the hottest days of the year.

Parents of the pupils from William Bellamy said the children sat for hours with limited water on coaches without adequate air conditioning or blinds.

The two coachloads of 10 to 11-year-olds were caught in long motorway delays after a school trip on Wednesday to Chessington World of Adventures.

Five ambulances and four emergency response vehicles were called to a service station on the M25 after several children complained of feeling faint, including one boy who suffered an asthma attack, a spokesperson for South East Coast Ambulance Service said.

Mum Terri Pierson said her 11-year-old daughter Chloe was “severely dehydrated” when she got back to Dagenham three hours later than expected.

“She had severe heatstroke and was shaking and complaining of a tight chest. I was on the verge of taking her to hospital.

“We haven’t had an apology from the school. I am fuming. They were on the coach for four hours with no water or shade. The school had no provisions with them.”

Another parent, Sarah Tinton, said her daughter Isla, 11, was given just a small cup of water by teachers and left to share what remained of her drink with three other friends.

“I’m absolutely disgusted with the school. The kids watched their friends being carted off in ambulances. We’ve heard they are still in hospital,” she said.

Barking and Dagenham Council published a statement on behalf of the school, which confirmed the air conditioning on the coaches was broken and the only ventilation came from open skylights.

But it said that “more than enough water” was available and staff had bought extra water for the journey.

A spokeswoman said: “The staff handled a very difficult and distressing situation very carefully and the discomfort and risk to the children was reduced due to the professional attitude of staff. A member of staff called an ambulance as soon as it was clear some children were feeling unwell.”