The Conservatives have called on the Scottish Government to provide full details of why infrastructure projects funded using the Non-Profit Distributing (NPD) model have been delayed.
The Government announced a £2.5 billion NPD pipeline of projects such as new schools, roads and hospitals in November 2010.
NPD was developed as a finance model for privately funded infrastructure projects, and is an alternative to public private partnerships.
But recently the Government has faced criticism from the Conservatives for what they described as "weak" progress.
The Tories said the pipeline is projected to deliver only £20 million on the ground in 2012-13, compared with the £353 million projected in the 2011 spending review.
During a debate on the issue, the Tories will call for a detailed explanation of NPD delivery, and seek assurances that the current projections for 2012/13 and 2013/14 "will be either met or exceeded".
Finance spokesman Gavin Brown said: "Clearly the Scottish Government has messed up this project with considerable delays, but even now it is not clear why this has happened.
"We've had a number of single transferable excuses and, one-by-one, they have proved not to be true.
"We are using this debate to explore the issue further, in the hope if finally getting an explanation from the Scottish Government about why it has been so poor on delivery of these projects, especially at a time when the SNP said it was accelerating the process."