The 'concordat' between the NHS and the independent healthcare sector has sparked a sharp rise in health service work contracted to private hospitals.
BUPA Hospital Manchester general manager Stephen Bird said work from the NHS had 'stepped up threefold'.
His hospital had applied to vary its registration to allow 11 more beds to be used for paediatric surgery, due to increasing routine work from Manchester Children's Hospital trust.
But he added that he had received enquiries from all the city's trusts. 'There is a lot of work available to us if we wanted it from the other trusts.'
Mr Bird said occupancy at the BUPA hospital had been '100 per cent every day, all last week, all this week and all next week', compared with the 50-60 per cent occupancy usual in the sector.
Manchester Children's Hospital trust chief executive Stuart Smalley said the partnership with BUPA had begun before the concordat, 'because the work coming into the trust is becoming more and more complex and routine work is slipping'.
Bristol Royal Infirmary general manager Ben Bennett said his trust had a contract for 200 operations over three months with the BUPA hospital in Bristol, jointly negotiated with North Bristol trust.
His trust was 'not averse to partnership with the private sector' and had been using its convalescent beds for three or four years. But he added that there was 'a capacity issue' for the NHS in the area.
'It was well understood in the national beds inquiry that Avon was underbedded - We have made it part of our strategic case for development that we need to grow, not shrink.'
Industry analyst William Laing said the private sector would still only account for a small proportion of the NHS's work.
'It would make a bigger difference to the independent hospital industry rather than the NHS. It could significantly increase the amount of business they do in total.'