Gladstone Ports has denied it suspended a contractor who put Mr Shorten on the spot about tax breaks for higher income earners on the election campaign trail.

Mr Shorten's reply - "We're going to look at that" - sparked questions over Labor's tax policy during the opposition leader's campaign stop to the Queensland state government-owned operation on April 23.

The Courier-Mail on Monday said the contractor's pass failed to work the following day and the 49-year-old was told he was in breach for speaking to the media when he was filmed talking to Mr Shorten.

Mr Shorten told reporters on Monday he was not aware of the issue until the story appeared in the media, noting the company had put out a statement.

"People are allowed to express their opinions and they should be able to do so without fear or favour, full stop," the former union boss said.

Gladstone Ports Corporation said in a statement: "The individual, a subcontractor not a Gladstone Ports Corporation employee, was not in a position to speak with any knowledge or authority on behalf of the organisation."

The Courier-Mail said the worker, who has taken another job, did not want to publicly comment, but had been shocked when told of his suspension.

However, the ports corporation issued another statement later on Monday saying it did not suspend the worker.

"The port worker, a sub-contractor, is still employed by the contractor and carrying out work for their employer," it said.

"The worker is a sub-contractor, and as such GPC cannot comment on any decisions made by their employers."

It said it did not instruct any GPC employees or subcontractors to attend Mr Shorten's visit.

Australian Associated Press