The Environment Secretary has been warned that urgent action must be taken to protect Britain's rare chalk streams or they risk being lost "forever". There are up to 260 chalk streams in the world, with the vast majority (85%) located in the UK.

In a letter to Steve Reed, the CEO of charity WildFish warned the river are threatened by several issues such as pollution, development and over-abstraction. Nick Measham said: "We know that sewage pollution and abstraction are the main causes of the demise of chalk stream ecosystems.

"But environmental damage occurs because of an absence of controls and a real failure to admit the extent of the problem. In short, a failure to give protected status to chalk streams means that there is ineffective regulation of activities likely to cause damage."

Mr Measham, who warned the precious waterways could be lost "forever", said: "Government promises of future investment are not enough, especially where there are real threats from unbridled development facilitated by the Planning and Infrastructure Bill. What is needed is certainty of protection under the law, not compromise and vague promises."

A chalk stream is a river fed by groundwater emerging from chalk bedrock.

Abstraction - the taking of water from rivers - has long been a threat to these waterways.

Over-abstraction is a particular threat in times of drought as water companies will increasingly turn to removing water from already struggling rivers to help keep up with demand.

Campaigners have welcomed the government's plan to build two new reservoir projects in the next decade to reduce the reliance on vulnerable chalk streams.

But WildFish said more action must be taken in the meantime to help protect these habitats and the wild fish that call them home.

Mr Measham urged the government to designate all chalk streams as Special Areas of Conservation (SACs).

This designation would give the 161 chalk streams in England protections from key threats including water companies and businesses taking water.

The Government has been contacted for comment.