He said reducing the number of single occupancy vehicles using the bridges is “a major issue.”

“Phase one of the review is now complete and phase two will specifically consider the impact of future tolls on both the Tay and Forth road bridges, looking specifically at congestion, pollution and the environment,” he said in a written reply to Mid Scotland and Fife MSP Bruce Crawford.

At the end of last year the Scottish Executive abolished the tolls on the Skye Bridge.

There is speculation that ministers will agree to lifting the tolls on the Erskine Bridge to ease traffic congestion.

But ministers have pointedly refused to entertain suggestions that tolls might also be scrapped on the Tay and Forth bridges.

Now it appears the plan is to increase the cost of crossing what would be the last remaining tolled bridges in Scotland.

Mr Crawford, who is campaigning against increased tolls, said, “It is as clear as day from what the minister says that, far from being removed, toll charges on the Forth Road Bridge will only be increasing.

“With the introduction of congestion charging to enter Edinburgh, those using the bridge are in line for a double whammy.

“It is clear the Executive has no real overall strategy of how to deal with Forth Estuary travel matters and do not understand how motorists feel.

He added, “The question I am asking this close to an election is what is Gordon Brown doing to stop Fifers being fleeced.”

Helen Eadie is the MSP for Dunfermline East, the constituency represented by Gordon Brown at Westminster.

“If tolls are removed on the Skye Bridge not yet paid for, what equity and justice is there in continuing to demand tolls for those bridges in Scotland where they have been completely paid for over and over and over again?” she said.

Scottish Tory transport spokesman David Mundell said, “This is nothing short of a plan to take more cash from Scotland’s motorists who already pay the highest fuel duties and taxes in Europe.” Public protests over plans for a 25% increase to £1 for the Forth bridge toll ended with a two-day inquiry in December.