The Resources and Energy Minister, Martin Ferguson, has secretly pushed for increased surveillance by federal police intelligence officers of environmental activists who have been protesting peacefully at coal-fired power stations and coal export facilities.

Documents released to the Herald under freedom of information laws confirm the police are "continually monitoring" anti-coal mining and other environmental groups. Much of the intelligence collection is carried out for the federal police by a private contractor, the National Open Source Intelligence Centre, in Melbourne.

The documents reveal that Mr Ferguson, prompted by lobbying from energy companies, has urged stronger criminal penalties against protests that disrupt "critical energy infrastructure".

The Greens leader, Bob Brown, condemned the surveillance, saying it was "intolerable that the federal Labor government is spying on conservation groups" and wanting to "criminalise political protest".

Documents released by the Resources, Energy and Tourism Department reveal Mr Ferguson wrote to the then attorney-general, Robert McClelland, in September 2009 to raise "concerns of issues-motivated activism, and the possibility of disruptions to critical energy infrastructure sites".

Mr Ferguson sought advice on whether the resources of the attorney-general's portfolio, in particular the intelligence gathering services of the federal police, could be ''utilised to assist the energy sector and jurisdictional police to manage the increasing risk of disruptions".

In November 2009 Mr McClelland replied that while ''I recognise the right to protest, when actions jeopardise energy security and the delivery of essential services, it is important that measures be taken to prevent and deter unlawful activity".

He confirmed that the federal police continually monitored ''the activities of issues-motivated groups and individuals who may target establishments through direct action, or action designed to disrupt or interfere with essential services''.

Mr McClelland highlighted the role of the Australian Security Intelligence Organisation "in intelligence gathering, analysis and advice in relation to protest activity [that] focuses on actual, or the potential for, violence''.

"Where warranted, ASIO advice may take the form of security intelligence reports, notification of protest action or threat assessments.''

The documents show the energy security branch of Mr Ferguson's department ensured Macquarie Generation and Transgrid were warned of a "peaceful mass action" at Bayswater power station in the Hunter Valley in December 2010.

Police arrested 73 protesters who had occupied a railway line used to take coal to the power station. Most of the convictions were overturned on appeal.

Although most intelligence on protest activity comes from publicly available sources, the police confirmed that on rare occasions they conducted ''covert operations targeting individuals who may be members of [protest] groups where specific intelligence exists relating to criminal activities by those individuals".

Moves to criminalise protest actions arose after Brian Spalding, the chief executive of what was then the National Electricity Market Management Company, complained to the ministerial council on energy in July 2008 that existing penalties did not dissuade ''activists from illegal activity at energy infrastructure sites". Mr Ferguson referred the issue to the standing committee of attorneys-general, which undertook a review of relevant legislation.

Mr Ferguson's department has refused to release the committee's review of penalties, completed in November 2009, on the grounds that revealing "gaps and inadequacies" in the law would incite ''further protest activities".

Yesterday a spokeswoman for Mr Ferguson said: ''Governments at all levels are concerned to maintain energy security and economic activity. This includes maintaining the rule of law and energy supply where issues-motivated groups actively seek to engage in unlawful activity.''

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