POLICE spied on anti-fracking protesters and shared the information with Cuadrilla – a police blunder has revealed.

Sussex Police used covert surveillance to monitor the protests at Balcombe last summer, however it was supposed to be a secret redacted from published papers.

The slip-up emerged in a report compiled by Hertfordshire and Essex Police into the handling of the protests at energy company Cuadrilla’s test drilling site in Balcombe. It was released last week by Sussex Police in response to a request under the Freedom of Information Act. It includes a section that was redacted. However, the sensitive information could simply be revealed by changing the colour of the text in a Word document.

The part that was not intended to be released says: “Once the operation moved into August it was apparent that an appropriate range of intelligence sources were being harnessed, including where appropriate European Court of Human Rights (ECHR) compliant covert means.”

Sussex Police said last night that they were not prepared to disclose any specific details of the covert methods used, though they are understood to include undercover “covert human intelligence sources” and “electronic interception”.

Caroline Lucas, Green party MP for Brighton Pavilion, said: “I think it’s deeply shocking and a huge waste of police resources at a time when those resources are scarce. It looks like the police are trying to criminalise peaceful protest.

“The use of ‘covert means’ was excessive and intrusive. That is why I will be writing to Sussex Police tomorrow (Monday 23) to seek assurance that that this is not regular practice.”

Ms Lucas was arrested while taking part in a road blockade at the protest in August and later cleared of obstructing a public highway and a public order offence. Assistant Chief Constable Steve Barry said: "We disclosed the information in good faith and had made minor redactions.

"The reference to covert tactics is generic and does not compromise the operational effectiveness of our plans.

"We have a responsibility to gather intelligence to assess risk and build plans to keep people safe. Covert tactics are legitimate and necessary and whilst we can't disclose specific details the methodology of these tactics is well publicised.

"Where authorities are required these are ECHR - human rights compliant and all materials are handled in accordance with investigatory regulations."