Taxpayers are footing the bill for private finance initiative (PFI) schools with flagging pupil numbers, according to figures obtained by trade union Unison.

Brighton Council had to pay PFI contractors £4.5m when Comart and Media Arts School closed six years after being rebuilt.

Balmoral High in Belfast closed six years after it was built, when pupil numbers halved. The Northern Ireland Department of Education now owes the contractor £370,000 a year for the next 18 years.

Bishop Park College in Essex was completed five years ago and cost £25m. The school should accommodate 900 pupils but currently has only 550, so the council is consulting on proposals to turn it into an academy with a nearby school.

Last week, the government announced a £2.4bn fund, which will lend cash to private companies to ensure they continue to finance PFI schools planned under the £55bn Building Schools for the Future (BSF) scheme.

Margie Jaffe, policy officer at Unison slammed the government's plans, warning that PFIs offer poor value for money.

She said: "We know after the banking scandals that the private sector is not more efficient than the public sector. Where there are problems the public sector has to pick up the pieces."

She also criticised local education partnerships, which are long-term contracts between councils and companies involved in BSF.

She said: "These contracts give private companies exclusive rights to run public services for at least 10 years, but they're often not competitive."

Martin Freedman, head of pay, conditions and pensions at the Association of Teachers and Lecturers, condemned the government for allowing private companies to profit from education.

He said: "PFIs were introduced on the basis that private companies take on the risk associated with large building projects. But now it's the government who is actually taking the risk."

But Debbie Jones, chair of the Association of Directors of Children's Services' resources and sustainability policy committee, said local authorities are pleased about government plans to safeguard capital projects.

She said: "PFI is another mechanism to make sure we get the best quality public services, without the risk. The important thing is that it helps stimulate the local economy."