Federal Treasurer Josh Frydenberg has accused Bill Shorten of selling out blue-collar workers after the Labor leader told a voter he would “look at” cutting taxes for people earning $250,000 a year.

On the election campaign trail in Queensland, Mr Shorten was approached by a coal export terminal worker who said it would be good to see a tax break for higher income earners.

“We’re going to look at that,” Mr Shorten responded.

But Mr Frydenberg claimed the opposition leader had either lied or forgotten Labor’s “plan” to increase the effective top marginal income tax rate to 49 per cent.

“Did Bill Shorten lie or did Bill Shorten simply forget yet again about his higher taxes,” he told reporters in Melbourne on Wednesday.

The treasurer said Mr Shorten had “sold out” blue-collar workers who earn high salaries through overtime.

“He was too afraid, too cowardly to tell them he’s increasing their taxes.”

Under a Labor government, people earning more than $180,000 would pay higher taxes through a budget deficit levy.

Labor has previously promised to look at extending tax relief to high wage earners and those on the top marginal rate if and when the budget allowed it.

Labor frontbencher Ed Husic said the opposition had been upfront and honest about its policies and warned against reading too much into Mr Shorten’s comment.

He pointed to Labor’s ambitious tax reform plans, which include scrapping cash rebates to some Australian shareholders at tax time.

“From time to time we’ve been responsive as an opposition taking on the views of the general public,” he told Sky News.

“But I think we’ve been quite clear, quite open, quite detailed in what we’re going to do and that’s what you should stick with.”