Victoria Police has arrested a Victorian CFMEU organiser for trespass at a Footscray site earlier today.

The arrest follows Fairfax Media revealing today the federal government’s plan for a national police taskforce to combat crime and corruption in Australia’s building sector.

The union organiser is understood to have been arrested by police after refusing requests to leave the Victorian government’s regional rail site in Footscray this morning.

The organiser, who Fairfax Media has chosen not to identify, has also been accused by building industry sources of pressuring a builder on another government site, the Springvale Level Crossing Removal project, to use a particular labour hire company to supply traffic controllers and other workers.

The staff list belonging to the labour hire firm involved is understood to include the names of relatives of a promient Melbourne underworld identity.

Victoria Police has confirmed a 33-year-old Preston man was arrested at a McNab Road site in Footscray this morning. He is expected to be charged on summons with trespass, a police spokeswoman said.

The union organiser declined to comment when contacted earlier today. Comment is being sought from the CFMEU.

Attorney-General George Brandis is preparing to launch a police taskforce comprising the Australian Federal Police, the Australian Crime Commission and state police from NSW, Queensland and Victoria to work with the royal commission on union corruption.

In a move that broadens the commission's reach and ability to investigate union corruption, Fairfax Media has learned that Senator Brandis is preparing to sign off on the plan, which will attach police agencies to the inquiry led by former High Court judge Dyson Heydon.

The move comes amid dissatisfaction in senior ranks of the federal, Victorian and NSW governments about a perceived lack of action by police in investigating long-standing concerns about organised crime and corruption in the building sector.

The co-ordinating police taskforce will work with the royal commission as it investigates allegations of malfeasance and corruption in the health services, construction, transport, electrical and Australian workers unions.

The addition of a police taskforce is likely to mean that the royal commission will use extensive investigative powers including phone interception and coercive questioning.

Among the crime figures likely to be targeted over their connection to construction union officials will be Melbourne gangland identity Mick Gatto and his associate in Sydney, George Alex.

It's understood that Senator Brandis' office is preparing letters that will formally request the involvement of the NSW, Queensland and Victorian police in the investigation.

Over the past month, Fairfax Media has revealed evidence of bribery, organised crime and extortion and other forms of corrupt activity in the construction industry.

The revelations prompted the federal government to call a royal commission. At least three CFMEU officials have been removed following the airing of the allegations.

Senator Brandis first flagged the possibility of police agencies working with the royal commission, a proposal also flagged by Labor, when the inquiry was announced earlier this month.

For more details about the royal commission into union corruption, read Fairfax newspapers tomorrow.

For coverage of the issue so far, see our special index on the building racket.

If you have more information, contact: jmassola@fairfaxmedia.com.au