Labour have renewed pressure for NHS reforms to be scrapped after securing an urgent Commons grilling of the Government over Nick Clegg's backing for further changes.

Commons Speaker John Bercow granted a request by shadow health secretary Andy Burnham for an urgent question about the latest development in the drawn-out saga.

Mr Clegg, the Deputy Prime Minister, sought to head off a revolt within his Liberal Democrat party by endorsing moves to limit competition in the health service.

He issued a joint letter with Baroness Williams, the most prominent Lib Dem critic of the shake-up, as activists prepared to raise concerns at the party's spring conference next week.

Downing Street indicated that Prime Minister David Cameron had been consulted on the letter and was happy to sanction further changes to the flagship Bill. There would be no "significant" amendments however, Number 10 insisted, only moves to provide "reassurance and clarity" to coalition colleagues.

The Health and Social Care Bill has already been substantially altered amid strident opposition from many health professionals - with significant groups remaining hostile to the proposals.

Sources close to Health Secretary Andrew Lansley said he was "relaxed" about the changes sought by Mr Clegg, which he did not believe would substantially alter the impact of the legislation.

Labour dismissed the letter as a "panic move" by Mr Clegg to save him from confrontation with activists, who last year forced the Government to "pause the legislation" and make changes.

Mr Burnham said the "cosmetic" amendments fell well short of Lady Williams' earlier demand for the section of the Bill which deals with competition to be dropped in its entirety. It came as Reform, a centre-right think-tank, called for the competition provisions to be retained to improve "quality and productivity".

Mr Lansley will respond in person to the urgent question, his spokesman said, cancelling a speech to town hall leaders and patient groups in order to attend the Commons.