LOCAL AUTHORITIES, health trusts and other public agencies will end up paying up to twice as much as is necessary for the 700 developments planned or built under the UK government's Private Finance Initiative (PFI).

And private companies could pocket up to £50 billion in profits from investing in schools, hospitals and other public building projects through the scheme, an investigation by the Sunday Herald has revealed.

The revelations, based on tens of thousands of pages released under freedom of information laws, have confirmed critics' worst fears. They say PFI has turned out to be "a huge scam", "a total taxpayer rip-off" and "a cynical accounting fiddle".

Internal financial projections for six PFI schemes show investors are expecting to recoup 12 times more than they invested. In some cases shareholders are predicted to make truly astronomical gains.

Equity of just £100 invested in rebuilding Hairmyres Hospital in East Kilbride is projected to earn £89 million in dividends over 30 years, while half a million pounds of equity in the new Edinburgh Royal Infirmary is expected to win dividends of £168m.

PFI was introduced under the Conservative prime minister, John Major, in 1992 and later pursued by Gordon Brown after he became chancellor in 1997. It was designed as a way of injecting private capital into public projects in an attempt to get debts off the Treasury's books.

The idea was that capital would be raised on the private market to fund developments that would then be built and run by private firms. Although the projects would cost public authorities little up-front, they would then have to pay for them in instalments over the next 25 or 30 years.

Despite the fact PFI has delivered hundreds of new hospitals, schools, sewage works and roads across the country, it has provoked a prolonged storm of controversy. But until now, there has been little hard information on which to judge the schemes because they have been shrouded in commercial secrecy.

A series of recent requests under freedom of information legislation has, however, begun to lift the lid. For the first time the detailed analyses done for the backers of six PFI schemes, five in Scotland and one in England, have been released.

The resulting piles of paperwork have been studied over the last year by economists Jim and Margaret Cuthbert. Jim is a former chief statistician with the Scottish Office, while Margaret was an academic at three Scottish universities. Now the husband-and-wife team run their own consultancy in Edinburgh.

Using investors' own projections, the Cuthberts have calculated how much profit was predicted from the six schemes. As well as the new Edinburgh and Hairmyres hospitals, they included the James Watt College campus in Kilwinning, 11 Highland schools, new Perth and Kinross Council offices and County Hospital in Hereford.

After stripping out the payments made for servicing the buildings and the normal commercial lending by major banks, the couple uncovered what they describe as "eye-catching" returns. They have submitted their findings to the investigation into the funding of capital projects being carried out by the Scottish parliament's finance committee.

Overall, the Cuthberts found that £42m of "subordinate debt" invested by the companies building the six schemes was predicted to yield £517m. Included in that, the profits on the £717,297 put in as equity by shareholders were projected to reach £350m.

They calculated that the internal rate of return being earned by investors varied from 17% to 23% on debts that were often more than double the capital invested. Even when the profits were converted to reflect the effects of possible future inflation, they look very healthy.

What's more, the Cuthberts' calculations suggest the projects are very poor value for money. The Edinburgh Infirmary, Hairmyres and James Watt College could all have been built for half the cost if the money had been borrowed in the normal way from the government's national loan fund, they say, and huge savings could have also been made on the Highland schools, the Perth offices and the Hereford hospital.

"What this suggests about the costs of PFI is extremely worrying," said Jim Cuthbert. "No country, whether it be Scotland or the UK as a whole, could long support funding its major public infrastructure on a one-for-the-price-of-two' basis.

"There has clearly been a systemic failure in the existing mechanisms designed to secure value for money from PFI schemes."

Detailed financial information on the vast majority of the 700-plus PFI schemes agreed across the UK is still confidential. But if their projected profits were only a proportion of those from the six schemes on which data is available, they could reach a massive £50bn.

On similar assumptions, the profit from more than 60 completed PFI projects in Scotland alone could rise to more than £5bn.