NHS nurses could strike if the Government threatens the payments they receive for working anti-social hours and weekends as part of David Cameron's drive to create a seven-day service, a nursing leader has warned.

In his first major speech since the general election produced a Conservative-only Government, the Prime Minister was set to assure the public that the NHS was 'safe in our hands' and to renew his vow to boost health funding by £8 billion by 2020.

As part of proposals to 'transform' health services around the country, Mr Cameron will promise more GPs, faster access to new drugs and treatments and a greater focus on mental health and healthy living. And he will say that GP and hospital care should be available to patients 'wherever they are and whenever they need it'.

Speaking at a GP surgery in the West Midlands, the Prime Minister will say: 'Our commitment is to free healthcare for everyone - wherever you are and whenever you need it.

'That means getting the best care and making that care available for everyone - free - wherever they are and whenever they need it.

'So I believe that together - by sticking to the plan - we can become the first country in the world to deliver a truly seven-day NHS.'

Royal College of Nursing (RCN) chief executive Peter Carter warned that nurses would resist any changes to payments they receive for working outside office hours.

Dr Carter told the Independent: 'I would particularly give a really strong warning to the Secretary of State: any attacks on unsocial hours, weekend working payments, would be strongly resisted.

'The membership is quite clear: unsocial hours, weekend working, Christmas Day and bank holidays - they get a very modest higher level of remuneration. Any attack on that and I do fear it would result in industrial action.'

But Health Secretary Jeremy Hunt accused the RCN of 'jumping the gun'.

Mr Hunt told BBC1's Breakfast: 'We haven't made any proposals whatsoever about changing nurses' terms and conditions ... Eight days into a new Government, I hope you'll forgive me if I don't negotiate on air about every single aspect of doctors' and nurses' conditions. That's not our proposal.

'I think the RCN should talk to their members and, rather than grandstanding like this, should come and talk to me. They want the NHS to be the safest in the world, I want that and it's what patients who use the NHS want, and I'm sure if we work together we can find a way of delivering that.'

The Tories made clear during the election campaign that they supported a plan produced by NHS England chief executive Simon Stevens to fill a funding gap estimated at £30 billion a year by 2020.

The scheme would see £22 billion of efficiencies, with the remainder coming from government coffers.

Mr Cameron was expected to describe the health service as the embodiment of 'One Nation' politics, and promise 'a seven-day NHS, safe in our hands - for every generation to come.'

Downing Street aides said the GP Access Fund set up under the coalition was already extending opening hours, and the shift to seven-day services would help save lives.

However, Mr Cameron is expected to deny that staff will have to work longer hours - arguing that instead there needs to be a more flexible approach to work patterns so doctors and nurses are available at the right times.

BMA council chairman Dr Mark Porter said: 'Crucially, the £8 billion promised by the Prime Minister is the bare minimum needed for the NHS to simply stand still and will not pay for extra services.

'The real question for the Government is how they plan to deliver additional care when the NHS is facing a funding gap of £30 billion and there is a chronic shortage of GPs and hospital doctors, especially in acute and emergency medicine, where access to 24-hour care is vital.

'Without the answer to these questions this announcement is empty headline-grabbing and shows that, even after polling day, politicians are still avoiding the difficult questions and continuing to play games with the NHS.'

Mr Hunt acknowledged that seven-day working would involve 'some extra cost which we will have to find', but said it might be more cost-effective, for example, to use boost capacity by using existing operating theatres at weekends, rather than building new facilities to use Monday to Friday.

'We know that up to 3,000 people lose their lives every year because they don't get the proper clinical cover they need at the weekends,' said the Health Secretary. 'The NHS is the first system anywhere in the world that's saying this is a problem, and we want to do something about it.'

He added: 'We need an NHS that responds to changing consumer expectations. People don't necessarily want to have to take time off work to go and see a GP and that's why a seven-day GP service is also a very important part of what the Prime Minister is talking about today.'