In Fatally Flawed, a report criticising the reforms, Lord Owen warned that the Bill would ‘challenge vital aspects and principles of the NHS’.
He said the reforms would lead to an increase in litigation claims and damage the doctor-patient relationship.
Lord Owen, a Labour health secretary in the 1970s and later leader of the breakaway Social Democratic Party, said the Bill should not be enacted in its present ‘shape and form’.
He said: ‘There was no mention in either the Conservative or Liberal Democrat party manifestos at the 2010 general election of an intention to carry forward anything like this revolutionary change.
‘Under the Salisbury Convention the House of Lords is entitled therefore to make substantial amendments to this Health and Social Care Bill.’
He said the Bill must be amended to make clear that NHS commissioning will be exempt from competition law.
He said the ‘unlimited rise of competition and free choice’ would make it more difficult to integrate care and lead to an increase in legal claims.
‘Whatever ministers may assert to the contrary, the continued rise of competition and choice in the NHS will inevitably be matched by a rise in legal conflicts, and litigation costs for the NHS,’ Lord Owen said.
He also said it was ‘bizarre’ that the government was introducing the any willing provider policy while trying to make efficiency savings.
‘There is no escaping the fact that providing choice is expensive,’ he said.
Meanwhile, Lord Owen said the reforms could ‘irrevocably’ damage the doctor-patient relationship if patients fear GPs’ decisions are made on the basis of cost and not in their best interests.