ENGINEERS building the new road bridge over the Forth have revealed that its revised opening date of May is "realistic but not guaranteed" amid claims the public has been "hoodwinked" over the costs.

The Queensferry Crossing is due to open six months late this spring with bad weather blamed for delaying construction.

As of last month, the project was 94 per cent complete, with only one of 122 deck segments still to be lifted into place to complete the link across the Forth between the Lothians and Fife.

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Other works outstanding include four concrete pours, 20 stay cables out of a total of 200 to be installed and 20,000 square metres of waterproofing.

Engineers have said the planned timescale to complete the bridge is "credible" unless this winter weather is unusually severe.

It comes as ministers were accused of hoodwinking the public after it emerged almost £200 million of savings claimed for the bridge were nothing to do with the project.

Former finance secretary John Swinney previously boasted the savings were “testament to the efficient management and effective delivery” of the Queensferry Crossing.

However in a letter to MSPs, project director David Climie revealed £192m of the £245m fall in cost since 2011, or 78 per cent, was down to lower than expected inflation.

He told Holyrood’s transport committee the 2011 budget of £1.6 billion had included a “high end estimate of inflation of £237m”, while the current budget of £1.35bn put inflation at just £45m.

He wrote: “The saving due to lower than expected inflation is therefore £192 million.”

He said the remaining £53m saving was down to a reduction in risk factors as the project neared completion and involved “robust risk and project management” by the delivery team.

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In September 2013, when the SNP Government announced the budget had fallen £145m, it credited “successful management of the project and the delivery of key milestones.”

Scottish LibDem Mike Rumbles MSP said: “It’s been all smoke and mirrors from the Scottish Government. Nearly £200 million of the so-called savings has been down to inflated projections, rather than the ‘robust risk management and strong project governance’ reported to Parliament.

“Trying to deliberately hoodwink the public on both the timescale and cost of this major infrastructure project is simply unacceptable.”

Mr Climie also told MSPs he was “optimistic” the new 1.7 mile bridge will never have to close in high winds because of 5,700 metres of 3.5m high transparent shields.

Earlier this month, the existing Forth Road Bridge was forced to close for a day when a lorry was blown over despite the bridge being closed at the time to high-sided vehicles.

Mr Climie said: “The wind shielding on the new Queensferry Crossing will break up the wind so that it significantly decreases the pressure on high-sided vehicles.

"What it means is that if a high-sided vehicle can get to the crossing, it will be able to cross safely and not, as we have seen recently on the Forth Road Bridge, take a risk and end up with a significant problem.

"We're optimistic that the new bridge will never close but we can't guarantee that as who knows what might happen."

A Scottish Government spokesman said: “It is a simple fact that the project has released £245m worth of savings back to the Scottish Budget since construction began in 2011.

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“The £53m saved over that time specifically due to robust project management by the Scottish Government team is obvious evidence of a successfully procured and managed project.”