Plans to build a new £2.3 bn bridge over the Firth of Forth are expected to get final approval from Holyrood today.
MSPs are likely to back the necessary legislation for the crossing to be built when it comes before them this afternoon.
With some of the cables on the existing road bridge having been affected by corrosion, the Scottish government believes the project is vital to the country’s economy.
The new bridge is scheduled to be completed in 2016.
However, campaigners against the crossing are urging MSPs to consider postponing the passage of the Forth Crossing Bill.
Lawrence Marshall, the chair of the Forth Right Alliance, said it was “premature for the Scottish government to be hell-bent on signing contracts to build a new crossing”, when inspections of the main cable were scheduled to take place next summer.
He argued that the government should wait until a more informed decision could be made, which could save the country a “vast amount of money”.
Marshall said: “We thus call upon MSPs to consider either postponing passage of the Forth Crossing Bill or at the very least consider inserting a clause into the bill which will have the effect that it cannot be triggered until the results of the third inspection of the main cable are known.
“To sign a pre-election contract to build an additional crossing without this full knowledge is to play Russian roulette with the Scottish public purse – a needless risk and far from electorally popular.”