The State Opposition claims $280-million of unallocated Royalties for Regions money could be used to upgrade Western Australia's rail network.

The Premier Colin Barnett has refused to use tax payers money to fund the upgrade although the operator WestNet Rail has suspended operations on four of its lines.

The Opposition Spokeswoman for Regional Development, Alannah MacTiernan, says the importance of the rail network, which is used by WA farmers to transport grain to port, warrants Royalties for Regions funding.

She says road transport is not necessarily the cheaper option.

"It's bad for the farmers," she said.

"It's going to be bad for the tax payer. It's going to be a more expensive option ultimately for the tax payer. And it's going to create real road safety and amenity issues in our country towns and regional cities."

The Regional Development Minister Brendan Grylls has been contacted for comment.