Dredge spoil may end up being dumped in the Great Barrier Reef Marine Park if the Queensland government's plan to dump it onshore is knocked back.

The federal government has already approved a plan to dump 1 million cubic metres of spoil in the marine park, but the state government has proposed a plan B to deposit it on land.

That plan is now being considered by the federal government and challenged by the Alliance to Save Hinchinbrook in the Federal Court.

Premier Campbell Newman, on the election campaign trail in Townsville on Friday, suggested that it may be back to plan A if onshore dumping is knocked back.