The NHS's use of the 'extortionate' private sector has come under the spotlight following the revelation that a south London mental health trust ran up a deficit of almost £1m in two months, largely because of reliance on private beds.

South London and Maudsley trust reported a£944,000 overspend in the first two months of this financial year,£611,000 of which was due to using private sector beds as far afield as Manchester and York.

The trust had budgeted for 60 private beds per day, but averaged 87.

In May, 26 per cent of its patients were in private beds. The rest of the overspend went mainly on agency and non-trust staff.

The trust claimed this week that an 'overspills solutions package' had already had some success. It is confident that the end of June overspend will be less than the£1.5m recently forecast.

But Geoff Martin, campaigns director of London Health Emergency, said the 'major problems' of mental health trusts' reliance on the private sector could only be solved by capital investment from the government. 'The cost of providing care in the private sector is extortionate.'

Health secretary Alan Milburn suggested recently that use of the private sector would have only a small role in the national plan. But Peter Fermoy of the Independent Healthcare Association said Mr Milburn's 'concordat' with the private sector - which aims to increase NHS use of private sector spare capacity - was still in place.

He claimed that the costs of treating mental health patients in the NHS could be as much as in the private sector.

South London and Maudsley trust's borough director for Lewisham Tracey Gummer - who is also lead manager for the overspills solutions package - said a private bed cost the trust around£350 per day.

'They are, broadly speaking, 20 per cent more expensive than our own provision, because of course they do have a profit element. But what they are offering is not directly comparable.'

But she said that 're-directing the resources we are currently spending in the private sector into our own provision' remained central to the trust's recovery programme.

Other mental health trusts in the capital have already successfully reduced their use of private sector provision.