Figures disclosed to The Herald show that £574 million was paid to three companies – Scotland Transerv, Bear Scotland and Amey – under four separate contracts signed between 2006 and 2007, against a combined bid price of £338m.
Transport Scotland, the Government agency that oversees maintenance of the trunk road network, defended the rise, saying it reflected the cost of inflation and work not included in the original contracts.
The two harsh winters at the start and end of 2010 and high rainfall played a significant role in increasing the amount of maintenance work required as repairs were undertaken on potholes and roads closed by landslides and flooding.
A Freedom of Information request was made last year after a row between Transport Scotland and Amey, which lost out on bids to win two maintenance deals covering the west of Scotland worth up to £700m. These were deemed to carry "significant unacceptable risks".
Civil servants said the company had bid a far lower price than its competitors, including quotes to do 1500 jobs for just 1p, and would have faced a shortfall of £123m.
The figures show the biggest difference between bid prices and payments was for the north- west, where Scotland Transerv put in a bid of £78.5m – below Transport Scotland's budget of between £85m and £135m. The actual spend was significantly above budget at £176.2m.
Across all four contracts, the total spend was £2.1m below the upper end of the predicted budget range of between £312m and £576m.
Donald Morrison, head of asset management at Transport Scotland's roads division, said the additional costs included "non-priced" items in the original 2006/7 contracts that covered landslides and floodings as well as pothole repairs.
More money had been provided for projects to enhance the road network than had been originally budgeted for, he said. "We got very competitive bids and because of that could get more work done on some things than expected," he said.
A senior industry source said: "There may have been some sour grapes from Amey but it does seem like a big gap (between bid price and final cost).
"You can include inflation, some additional funding and winter maintenance but even then it doesn't quite reach the outturn cost. It's something that you would hope Audit Scotland would have a look at."