Lally said the weekend's fly-tipping was "one of the worst examples that we have come across", but it was not unusual to find discarded BBQs, beer cans and rotting food.

"Logic says it's lighter to carry back once you've eaten and drank it all than it is to carry it out there," said Lally.

"Come and have a nice time, but leave no trace."

She said the phrase "leave no trace", cited in the code, had been associated with beauty spots "for so long" but was "just as relevant today".

The Countryside Code also states that "dropping litter and dumping rubbish are criminal offences".

"Our wardens have gone from supporting firefighters with the wildfires and, the first rainy weekend, they're off finding abandoned wild camps. They have had quite the summer," said Lally.

"It has a knock-on effect on wildlife. There's still a fire risk. Pollution can contaminate water. It affects everything, not just it looking nice."

Steffan Edwards is a warden at Bannau Brycheiniog National Park and cleaned up the mess.

He told BBC Radio Wales Breakfast: "We've got plenty of things to get on with within the national park as warden's.

He said it was a "shame to see all that rubbish discarded on the hill" but added warden's like Edwards discover abandoned items "all the time", which they have to deal with.

"This isn't new to us and it's not new to other national parks and other beauty sites across Wales and the UK. But what we are finding is it's an increasing problem over the last couple of years.

"People are finding out about these nice places and taking literally everything up with them, which you would take to a campsite and just leaving it there."

Policy and Advocacy Manager at Wildlife Trust Wales, Joe Wilkins, said the discovery of the litter has come at a time where plants and animals "can't sustain another threat", following a summer of extreme heat.

Wilkins said it is "so important that people have access to these spaces" and the ability to enjoy them, adding it is "unfair" for people to "absolutely ruin that experience for others".