The WA Transport Minister could be dragged into an ASIC investigation of suspicious share trading.

The corporate regulator is looking at trades linked to the Perth airport rail project and a potential information leak.

ASIC has requested documents and phone records from Transport Minister Dan Nalder’s office as part of its look into the leak.

Mr Nalder has confirmed his office handed over documents to ASIC as part of its examination of unusual trading related to the Forrestfield Airport Rail Link.

The inquiry was launched when the share price of NRW Holdings jumped 30 per cent on February 15.

It was just three days before announcing that its joint venture had won preferred bidder status for the $2 billion project.

The company says it only became aware it was selected after trading closed on February 17.

Mr Nalder said there was no wrongdoing on his end.

“There were staff that were involved from time to time in specific meetings, but all my staff were specifically excluded from anything to do with the final proponent and the prices,” he told the ABC.

“My staff were only advised — and I've double and triple checked that... only became aware [of the preferred bidder], when I became aware.

“There is no accusation from ASIC or ASX that anybody, anywhere within the State Government has had any involvement in any wrongdoing.”

The WA Opposition has continued to call for a separate Government inquiry into the actions of public sector employees related to the issue.

“This is one of the most serious matters I've seen in politics where we have a ministerial office being investigated for leaking information about a successful tenderer,” she said.

“We asked the Minister about this issue in February and he denied his office knew about the awarding of the tender until just the day before.

“I think it's pretty clear that the information was leaked, so the question is where from.

“It was up to the Minister to come into the Parliament and tell us that his office and his agencies were being investigated, he hasn't and we will be asking the Minister a serious of questions today about exactly what he's known about the ASIC investigation and how many people knew about the successful bidder before it was announced.”

The Opposition has been firing shots that the Transport Minister for some time, accusing Mr Nalder of mismanaging his portfolio by shelving the MAX Light Rail project.

It has also criticised his support for a controversial underground rail tunnel link proposed for Perth's northern suburbs.

The Minister is now under fire for the heavily-delayed Perth Freight Link project, which not seen any progress for over a year, since the WA Supreme Court ruled the environmental approvals for Roe 8 were invalid.

The ruling could even force the Government to conduct a new tender process for the project, despite having selected its preferred bidder.