Clark told Third Sector that delays in the publication of the spending watchdog's report, called Building Capacity in the Third Sector, were unacceptable, and has this week tabled a parliamentary question asking ministers when it will surface.
"There are lessons that need to be learned from what has gone wrong," he said.
Clark told delegates at a sector conference in Nottingham last week that "mistakes had been made" by government in initiatives such as the ChangeUp infrastructure programme, run by Capacitybuilders.
The NAO report on capacity building programmes was originally scheduled for early 2008, but the publication date was put back (14 May, page 1), with no date for publication now set.
A spokesman for the NAO declined to comment on Clark's remarks and said the organisation would decide its own publishing schedule.
- See Editorial, page 12.