Ed Miliband will seek to turn the screw on David Cameron over controversial NHS reforms today by accusing him of “betraying” Britain’s proudest institution.

Amid speculation that the radical plans are set to be watered down, the Labour leader will say the coalition’s policy has descended into “utter confusion and chaos”.

He will dismiss the Health and Social Care Bill as “broken”, and offer cross-party co-operation to develop replacement proposals.

The attack comes as Mr Cameron and Nick Clegg prepare to launch a “listening exercise” later this week in a bid to reassure critics of the shake-up, which will see GPs handed control of commissioning services.

However, government sources denied they were considering fundamental concessions, or that ministers wanted to “press the pause button”.

A Downing Street spokesman said: “The government is utterly committed to the NHS and its principles. We are also committed to modernising the NHS. Progress on the ground continues to be impressive.

“The speculation is ill-informed and filled with inaccuracies. The bill has now successfully finished committee stage in the Commons and there is a natural break before it moves to the Lords.

“We have always been prepared to listen, having already clarified that there is no question of privatisation and that competition will be based on quality, and will continue to do so.”

Concerns have been growing about a public backlash against the flagship bill, with doctors lining up to criticise key elements.

The Liberal Democrat leadership is also struggling to appease the party’s grass roots, who overwhelmingly voted to reject the plans at spring conference last month.

Delivering a speech in London, Mr Miliband will complain that after “sustained and substantial improvement” under Labour the NHS is suffering because of desperate “horse trading” between the coalition partners.

“It is bad government. It is not how the future of the health service should be determined,” he will say, whiel urging the coalition to rip up the bill and produce a new white paper.

He will say: “My commitment is this: if there is a genuine attempt to address the weaknesses of this top-down reorganisation then my party will enter into a debate about a new plan with an open mind and accepting that any NHS plan must be delivered within a tight spending settlement.”