Increasing the amount of money NHS hospitals can earn from private patients could have "catastrophic" effects, a Liberal Democrat MP has warned.
Andrew George, a member of the Commons Health Select Committee, said he did not believe ministers fully understood the consequences of the move.
The MP for St Ives, who has been a prominent critic of the Government's controversial NHS reforms, warned that it could lead to a legal battle with private healthcare providers.
The Health and Social Care Bill removes the cap on the amount of private income foundation trusts can earn.
Mr George warned: "If NHS foundation trusts ... can muscle in on the private market then private providers will feel more justified, and the courts could well agree, in arguing the right to compete for far more NHS services."
He said "pay beds" in NHS hospitals represented a challenge both ethically and in terms of competition law.
Mr George told the Commons: "Once you go down this particular road there's a lot of conundrums which arise which need to be sorted out.
"I don't believe the Government entirely have a handle on this issue."
He accepted that the Government was not attempting a stealthy privatisation of the NHS but warned there could be unintended consequences.
He said: "I don't think, as some people are claiming, that ministers are wanting to push privatisation across the NHS, I think their intentions are honourable. But I think that this could end up being a catastrophic policy and it could unleash something which, once it goes through, we can regret these mistakes at our leisure in future."
