Liberal Democrats will block the government’s NHS reforms unless they secure significant concessions, deputy prime minister Nick Clegg has said.

His threat came as Mr Clegg said he was determined to give the Liberal Democrats a “louder voice” in the coalition in response to their drubbing in the polls last week.

The Lib Dem leader made clear his first battle will be over health secretary Andrew Lansley’s plans to hand NHS commissioning power to GPs and increase the scope for private provision within the health service.

Unless there are “substantial, significant changes” to Mr Lansley’s proposals, he said he will tell Liberal Democrat MPs and peers to vote them down.

“I am not going to ask Liberal Democrat MPs and peers to proceed with legislation on something as precious and cherished - particularly for Liberal Democrats - as the NHS unless I personally am satisfied that what these changes do is an evolutionary change in the NHS and not a disruptive revolution,” said Mr Clegg.

Conservative ministers sought to smooth over rifts within the coalition following a referendum campaign which saw insults and accusations exchanged between Cabinet colleagues.

“There’s a lot of heat in an election campaign in any democracy. Of course things are said, but we’ve had the result and now we move on,” chancellor George Osborne told the Andrew Marr Show on Sunday.

Mr Osborne insisted that he and Mr Cameron also wanted changes in the NHS bill.

“We want to reassure people we’re not - and never have wanted to [privatise] - privatising the NHS. We believe in the NHS as a public service free at the point of use,” said the chancellor.