KPMG analysis of the pipeline shows that 28% of projects have disappeared since December 2014.
Most of the decrease comes in transport where £6.7bn of schemes are now missing and housing and regeneration schemes have seen a £2.8bn drop.
The acccountant said: “KPMG understands that the remarkable decrease in the number of projects is largely due to potential projects being removed from the pipeline to avoid pre-empting decisions in the forthcoming Spending Review.
“There are also a number of projects that have been completed since the December 2014 iteration.”
But the analysis also found that 1,784 projects did not specify a construction start date, further raising questions about the completeness of the data.
Richard Threlfall, KPMG’s UK Head of Infrastructure, Building and Construction said: “It is clear that more needs to be done to improve the consistency and accuracy of the Government’s construction pipeline.
“A stable pipeline would give the construction industry good visibility of future demand and the ability to plan and invest for that demand.
“It would lead to efficiencies for the Government and hence for the taxpayer.
“Instead we have a pipeline whose data is so incomplete, and which fluctuates so wildly and erratically that the industry can place no detailed reliance on it.
“I hope that we will get a clearer picture in November when the Spending Review is published. But in the meantime the huge 28% drop in the number of projects included suggests some Government departments are putting projects on hold in the expectation that they get culled.
“I don’t expect we will see anything like the scale of cutback in capital programmes that the industry experienced in 2010, after the last election, but there is clearly cause for nervousness about the potential squeeze in spending.
“I hope the Government will recognise that what this industry most needs is long-term certainty and stability in demand, to provide it with the confidence to invest in technology and its workforce.
“Our growing economy is creating a welcome uplift in private sector demand, but the Government should not use that as an excuse to cut back its own investments, create another hiatus, and send ripples of uncertainty through the industry.”