Five offshore PFI companies paid little or no corporation tax during a five-year period despite making profits of nearly £2bn, the BBC has learned.
The five companies specialised in lending money through Private Finance Initiatives (PFI).
They own hundreds of public assets including schools, hospitals and even police stations.
The BBC has also learned that a small number of big offshore companies are currently on a buying spree.
They are buying up a number of the UK's public buildings.
Research carried out by the think tank that investigates PFI deals, the European Services Strategy Unit, reveals the extent of the buy-up in Britain.
- Nine off-shore infrastructure funds own between 50% and 100% of the equity in 335 PFI/Public Private Partnership (PPP) projects. This amounts to 45% of all 735 current projects
- 12 offshore companies have bought equity in 74% of the 735 current projects
- Education and health projects, including schools and hospitals, account for two-thirds of the purchases by offshore companies
Meg Hillier, the Labour MP who chairs the Public Accounts Select Committee, told the BBC's The World Tonight: "Frankly it is shocking. Our taxes are paying for our schools and hospitals... and yet these companies are clearly profiting and paying no UK tax. I don't think that was ever envisaged when PFI was established."
Ms Hillier, MP for Hackney South and Shoreditch, also expressed concern at the concentration of so many public assets in so few hands offshore.
"I think nobody foresaw this sale of the debt on to companies and this conglomeration. Now we have so few companies owning such a large amount of the debt and that is a big concern."
She described UK public assets as a "cash cow" adding: "Now there is a very big gap between the owner of the debt and the service and organisation paying for it."
Dexter Whitfield heads the European Services Strategy Unit which carried out the PFI research for public bodies and other organisations.
He said offshore companies were making huge profits from buying public assets, with annual average returns on their PFI investments as high as 28%.
But Mr Whitfield said the companies paid little or no UK corporation tax despite making huge profits.
He said: "PFI is essentially a private sector profit machine. If the government adopted a strategy of building the public infrastructure directly through public investment and operating it through their in-house services this whole edifice would not exist.
"All these transactions are a product of the fact that there is so much money to be made in PFI."
Mr Whitfield said five offshore PFI funds made profits of £1.83bn over the five-year period ending in April 2015, but paid little or no corporation tax.
However, this was disputed by one offshore PFI giant, HICL Infrastructure Ltd, based in Guernsey.
It said Mr Whitfield's research took no account of the fact that tax was paid both by the company's subsidiaries and by shareholders on their dividends.
A spokesman said: "At the project level, HICL invests in a number of companies, which are incorporated in the UK and accordingly taxed by HMRC."
Meanwhile, many PFI deals are causing headaches across public services, particularly in the NHS.
The University College London Hospital's NHS Foundation Trust (UCLH) told the BBC that its PFI debt was far too high, mainly due to interest rate charges of between 7% and 8%.
This meant an annual bill of £30m, at least double what he believes UCLH could be paying if the debt was re-scheduled.
Professor Marcel Levi, UCLH Chief Executive, told the BBC: "If we spend an enormous amount of money on paying interest rates and this PFI debt, then that's money we cannot spend on patient care, on nurses, on treatment and management systems."
And it's money that is not being spent on achieving targets for A&E and cancer waiting times, he added.