Andrew Lansley should be prevented from implementing any further changes to the NHS while the Health and Social Care Bill is being debated, Lord Owen has said.

In a letter to cabinet secretary Sir Gus O’Donnell, the cross-bench peer expressed concerns about the constitutional implications surrounding the bill.

Guidance suggests arrangements can be made to bring in changes which would then be reversible if Parliament decided to amend the legislation.

But, in his letter, Lord Owen points to the way some primary care trusts have already being dismantled while appointments have been made to a new commissioning body.

He added: “It is obvious from constant briefing that the government is considering the bill as a whole with a view to making amendment before it reaches the House of Lords.”

Prime minister David Cameron and deputy Nick Clegg are launching a “listening exercise” this week following intense criticism of the shake-up.

Lord Owen said: “If the listening is to be meaningful, then the bill cannot continue to be pushed relentlessly by the secretary of state without Parliamentary authority.

“You will be aware that 90 per cent of the country is already covered by the new arrangements within the legislation.

“It is also the case that a shadow NHS Commissioning Board was due to start operation on 1 April as a special health authority.

“I would submit to you that, in the light of the briefing the government has been giving to the press about a delay in proceeding with the Health and Social Care Bill, it is necessary for the secretary of state for health to now cease implementing some aspects of the bill.”

Lord Owen pointed to three specific areas, with the first being that the “continued suspension of PCTs should be stopped”.

He added: “Secondly, public money should no longer be made available for redundancy payments to people employed by PCTs and, thirdly, the full planned start of the NHS Commissioning Board should be postponed, including any further appointments.”