Government officials investigating illegal dumping will go to the High Court in attempt to win similar intrusive surveillance powers to MI5.
The Environment Agency wants its investigators to be able to trespass on private land and bug vehicles.
"They are a useful tool," a spokeswoman said.
The agency today blamed dodgy advice from the Home Office for its earlier use of such techniques, which the Chief Surveillance Commissioner declared may be against the law.
A spokeswoman denied claims in The Daily Telegraph that the agency had continued to use such surveillance techniques despite Sir Christopher Rose's opinion that "any such deployment on a vehicle or property not owned by the agency would constitute Property Interference – which of course the agency was not empowered to do under the Police Act 1997".
The Environment Agency spokeswoman said investigators had suspended use of the techniques when Sir Christopher made his criticisms a year ago.
"We stopped immediately," she said. "The Home Office advice turned out to be incorrect."
Further claims the agency is setting up "a national spy network" were "rubbish", she added.
Investigators however want to restart intrusive surveillance operations and are now awaiting a High Court judgment to settle the legal argument.
According to documents seen by The Daily Telegraph Sir Christopher had in 2007 told the agency to get better legal advice, but at his next inspection last year found the situation unchanged.
"When I raised this matter with the Chief Prosecutor he was disappointed that trespass was still occurring," he said.
While the Environment Agency is among hundreds of public bodies mandated to carry out surveillance under the Regulation of Investigatory Powers Act (RIPA), it cannot obtain warrants under the Police Act to interfere with private property during operations. That power is reserved for police, customs and the security services.
The Home Office is currently reviewing RIPA after controversy over allegedly disproportionate use of powers by local authorities. ®