Shocking pictures show Britain's biggest ever fly tip - a pile of waste 500FT long dumped in one go.

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 in Oxfordshire.

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 told the BBC: "This is an environmental catastrophe unfolding in plain sight."

"Every day that passes increases the risk of toxic run-off entering the river system, poisoning wildlife and threatening the health of the entire catchment.''"

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 has meant 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 on Thursday, 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."

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.