In what a Federal Court judge described as behaviour more akin to a James Bond movie, the court heard this morning that industrial relations consultant Grace Collier hid a recording device in her bra to tape a conversation with union organiser Tony Mavromatis.

Lawyers for the Fair Work Building and Construction inspectorate conceded that one of the recordings Ms Collier made may have breached the law.

But they used the recordings from the device hidden in the bra as part of their case against Mr Mavromatis and the Australian Manufacturing Workers Union.

Lawyers for the union argue this recording was also in breach of the law.

The AMWU has denied any link to the eight-day blockade at the $40 million City West Water project, arguing that protesters had gathered at the site of their own volition.

Lawyers for the inspectorate argued that Mr Mavromatis was co-ordinating the protest and trying to coerce contractors to sack foreign workers - a breach of the law.

Central to the dispute is four Filipino workers hired on 457 visas by a contractor on site, with protesters saying the work should be done by locals.

In recent days, contractors have used helicopters to fly workers over the protesters and to allow some work to take place.

In the recordings, Mr Mavromatis tells Ms Collier – who is engaged by contractors on the site – that he can make the picket go away if the contractor employs local labour.

"Grace, give these blokes a job and the picket will end," he said. "I will give you certainty."

At another time, Mr Mavromatis agrees to a request from Ms Collier to try to secure the release of a security guard trapped on the site.

Lawyers for the AMWU said Mr Mavromatis was not organising the protest, rather acting as a conduit between protesters and contractors.

He was merely responding to requests from Ms Collier, they argued.

Justice Shane Marshall said there was an "element" of Ms Collier, an Australian Financial Review columnist, trying to set up Mr Mavromatis.

Later Justice Marshall criticised Ms Collier's conduct.

"Did she think she was in a James Bond movie? I have great concerns about Ms Collier's evidence."

The hearing also heard that at other times Mr Mavromatis is alleged to have approached the owner of Briagolong Engineering, Chris Lupton, with a crowd of protesters gathering around in what was described as a "highly intimidatory" situation.

Mr Mavromatis is also alleged to have told him to "get rid" of the four Filipino workers on 457 visas.

The hearing heard allegations of threats directed at contractors from protesters, including one to perform a "Columbian necktie" - a reference to slitting someone's throat.

Justice Marshall said he would reserve his judgment and publish his reasons as soon as possible.