A public inquiry into proposals to raise the toll for cars on Bristol's Clifton Suspension Bridge - from 30p to 50p - opens on Tuesday.
Opponents say there is 'no justification' for the toll rise
The bridge trustees say the rise is needed because of increased insurance charges, the cost of new lighting and the discovery of voids under one tower.
But the National Alliance Against Tolls claims the trust has large reserves and very little is spent on maintenance.
The toll charge for cars last rose in 2003, from 20p to 30p.
John McGoldrick from the National Alliance said it was "particularly opposed" to the increase and that there was "no justification" for any increase, let alone one of 66%.
"Very little of the tolls is spent on bridge maintenance - it seems to largely be spent on things like historical conservation, illuminations, administration and of course the cost of collecting the tolls," he said.
In a statement Clifton Suspension Bridge Trust said: "Current projections mean that, without an increase in the cash toll, there are expected to be ongoing deficits every year, with expenditure exceeding income."
It also pointed out in accordance with the Clifton Suspension Bridge Act 1952 the Trustees have to provide a reserve fund "...to cover any extraordinary claims or happenings".
The public inquiry starts at 1000 BST at the Avon George Hotel.