The cost of a return car journey across the Severn bridge is set to rise 20p to £5.10 from 1 January.
Lorry drivers will have to pay £15.30, a rise of 60p. One haulage contractor said he could not absorb the increase and would be forced to passed it on.
A spokesman for Severn Rivers Crossings defended the increase and said the increase was a fair deal.
"The price reflects the cost of the second crossing which the government decided would be paid for by tolls".
The bridge tolls - which are only paid on the Wales-bound journey - are governed by the Severn Bridges' Act, 1992.
The Act sets down the precise method and base prices for setting toll levels and the adjustment to next year's toll levels.