The Federal Opposition says a cement company could scrap a billion-dollar expansion in central Queensland because of extra costs imposed by an emissions trading scheme.

Nationals Senator Ron Boswell says the scheme would add $20 million a year to costs in the cement industry and Cement Australia is having second thoughts about a new plant in Gladstone that would have created 60 new jobs.

Senator Boswell says the Gladstone plant is owned by three multi-national companies, who could increase imports to meet demand for cement.

"They don’t have to produce cement here, they can do it elsewhere where there is no emission trading," he said.

"The threat is as these plants or new plants are developed, there is a prospect of a new plant developing here - and an extension - now that is seriously under threat, and as the plants wear down, whether they’ll be replaced, that’s also under threat."

He says emissions trading would have an impact on the industrial city.

"Cement is only a case in point; aluminium and alumina down in Gladstone would be suffering a similar fate," he said.