Government plans to allow private firms to take over the management of struggling NHS primary care trusts and hospitals have been roundly criticised.
Under the plans, about 20 NHS trusts which are falling short of minimum standards on quality, safety or finances are due to be identified as candidates for takeover. The first - Hinchingbrooke in Cambridgeshire - is already understood to be searching for new management, which could come from the private sector.
But Paul Kenny, general secretary of the GMB union which represents NHS staff and ambulance drivers, said the union "will resist this move with every sinew".
The BMA also said it had "grave concerns" about the plans. "This is part and parcel of the market in healthcare which brings winners and losers, and in those losers the government is bringing in the private sector - effectively privatising part of the NHS," a spokesman said.
The Department of Health stressed that contracts with private firms to provide management services at NHS trusts would not involve the transfer of NHS assets or staff to the private sector.
Officials said there were not expected to be "huge numbers" of cases of private companies taking over the management of NHS trusts.