Barry White, chief executive of the Scottish Futures Trust (SFT), claimed the body had saved the taxpayer more than £132 million, and, he said, although some projects had been delayed this was often because further savings were being made.
The trust was set up by the SNP Government in 2008 to find an alternative to the widely discredited public finance initiatives (PFI) and its successor public-private partnerships. These schemes had proved poor value for the public purse in paying for new capital projects.
Although the trust made significant savings (which were externally validated), its alternative to PFI, the Non-Profit Distributing model (NPD) has been criticised for delays in delivering supposedly "shovel-ready" projects.
Finance Committee convener Kenneth Gibson asked Mr White: "Are you not concerned this achievement has been overshadowed? Have you been over-ambitious and left yourself open to some of this criticism?"
Mr Gibson said there had been a "consistent overestimation of projects" and that every year there was "a huge imbalance between what is projected and what is achieved".
Mr White insisted that although there had been delays, NPD would see a "pipeline of investments" with a combined value of £808m, and due to start construction in 2014-15, which would bring benefits for many years to come.
He gave as an example of a worthwhile delay a planned secondary school which was held up because the local authority had decided to build a primary school on the same site using shared sports and dining facilities. This, he said, would provide greater value for money.
The Conservatives were scathing about the SFT's performance prior to Mr White's appearance. They pointed out that of proposals worth around £2.5 billion - including the Sick Children's hospital in Edinburgh and road improvements such as the M8 completion and the Aberdeen peripheral route - work had so far begun on only £270m worth of projects.
Labour MSP Michael MacMahon put it to Mr White that many projects dated back to announcements in 2006 by the former Labour-LibDem coalition.
Mr White also blamed delays on a cut in capital spending, which the current Scottish Government had sought to address with transfers from revenue spending.
l Ministers opened two new secondary schools yesterday. The Lasswade Centre in Midlothian and Eastwood High School in East Renfrewshire were built in partnership between the two local councils, helping to save an estimated £4m.
First Minister Alex Salmond opened the £36.8m Lasswade development which includes a swimming pool, library and other facilities for the general public.
"Lasswade High pupils are developing their skills and talents in a wonderful environment, including bright, airy classrooms and social spaces, and with excellent, fully equipped sports facilities," he said.
Education Minister Alasdair Allan opened the £29 million Eastwood School in Newton Mearns, which also has wider community facilities. "The new sports centre and two all-weather pitches will benefit not just the pupils, but the entire community," he said.
The £1.25bn Schools for the Future programme will lead to the construction of 67 schools across Scotland.