Shocking video shows Britain's biggest ever fly tip - about half an hour away from Banbury

The massive heap of hazardous rubbish stretches 150m and is around 20ft (6m) deep.

It was illegally dumped in a field next to the A34 and River Cherwell near Kidlington.

The waste was left in one go and described by an MP as "threatening an environmental disaster".

It was discovered last month by horrified anglers and contains plastic, foam and wood.

Charity Friends of the Thames said: “This is an environmental catastrophe unfolding in plain sight.

W"A mountain of waste has been allowed to build up just metres from the River Cherwell — an illegal landfill sitting on the floodplain of one of our most important waterways.

"Every day that passes increases the risk of toxic runoff entering the river system, poisoning wildlife and threatening the health of the entire catchment. The Environment Agency must act now, not in months or years, which is their usual reaction time.

"This is exactly what happens when environmental crime is ignored — and it’s our rivers, wildlife, and communities that pay the price.”

The Environment Agency has confirmed a probe has been launched and has encouraged anyone with any information to get in touch as soon as possible.

A spokesperson said: “The Environment Agency is aware and investigating.

“If anyone has any information then please call independent charity Crimestoppers anonymously on 0800 555 111."

It is hard to distinguish any particular bits of waste as it appears to have been shredded with earth mixed in with it all.

Some of the rubbish has fallen down because it was so tall, which means the proximity to the river is about five metres.

Calum Miller, Liberal Democrat MP for Bicester and Woodstock, raised the issue in Parliament.

Addressing MPs, he said: "Criminals have dumped a mountain of illegal plastic waste... weighing hundreds of tonnes, in my constituency on a floodplain adjacent to the River Cherwell.

"River levels are rising and heatmaps show that the waste is also heating up, raising the risk of fire.

"The Environment Agency said it has limited resources for enforcement, that the estimated cost of removal is greater than the entire annual budget of the local district council."