The report, from the National Audit Office, said that public authorities paid over £180 million for alterations to existing contracts, but were not given value for money, particularly on smaller changes.
For example, some authorities were charged up to £300 to fit an electrical plug socket, while others paid around £30.
In one case, a contractor put up a notice board for free, but in another, the authority was charged almost £150.
The report laid most of the blame not on contractors but on public sector management.
It said: “Larger changes were not always competitively tendered; the cost of making smaller changes was relatively high, varied widely across projects for similar work and took longer to process than in non-PFI projects; and almost half of the changes were completed later than the agreed timeframe.”
Edward Leigh MP, chairman of the committee, said: “Changes during a 25 to 30 year PFI contract are inevitable but they should not be costing the taxpayer an arm and a leg.
“Public sector contract managers must be a lot more street-wise. In the case of larger changes, they must insist on at least three competitive tenders.
“For all changes, they must be eagle-eyed that the contractor is not charging inappropriately high fees. The public sector has allowed itself to be taken for a ride.”
He said that public sector managers did not have the expertise to negotiate with their private sector counterparts.