Toll New Zealand is warning of big delays if industrial action by track maintenance workers continues for much longer.

Passenger and freight services have been cancelled or delayed, while workers from Ontrack, which runs the rail network, refuse to work overtime because of a pay dispute.

Toll spokeswoman Sue Foley says passengers and businesses are being caught up by the dispute which does not involve any Toll staff.

She says the situation should worsen if bad weather blocks railway lines and workers are not on the job to clear it.