A mass programme of health checks for over-40s in England will be launched this week, with ministers promising it will save 650 lives a year.
Every five years, those aged 40 to 74 will be offered blood pressure, weight and cholesterol checks alongside lifestyle advice.
But doctors and public health experts said the programme was not being properly co-ordinated.
GPs also said such checks were already done by targeting the most at risk.
Nonetheless, ministers are confident the programme will help prevent thousands of heart attacks and strokes each year and, as a result, save lives.
The success of the programme will depend on encouraging those people with unhealthy lifestyles who traditionally shun health services to come forward.
GPs currently carry out checks on about 80% of the age group.
The government hopes by launching a universal system they will reach those that are missed.
Local health chiefs will launch the programme on 1 April by writing letters to some of the most at risk groups, such as deprived communities and some ethnic minorities, inviting them for checks.
In total, more than 2m people will be assessed each year and and then re-called every five years.
Those found to be at risk will then be referred on to the most appropriate services.
The programme was first announced by Gordon Brown at the start of 2008 as part of a new year blitz of measures.
Health Secretary Alan Johnson said the programme was part of the NHS's attempt to focus on more preventative measures.
"I would encourage people to accept their invitation to a health check when they receive them - the checks will provide people with a personal assessment and tailored health advice that will help them make healthy choices."
The move has been warmly welcomed by medical charities, but doctors have expressed some doubts.
Dr Richard Vautrey, deputy chairman of the British Medical Association's GPs committee, said: "At the moment we have targeted checks aimed at the most at risk.
"Some people are missed, but I am not sure these groups will be coming forward for these checks."
Dr Vautrey said the programme could also lead to duplication because of the different health services that will be offering the checks.
They include GPs, pharmacies, health clinics and walk-in centres, although the government says this will help the programme reach out to all sections of a community.
Professor Alan Maryon-Davis, president of the Faculty of Public Health, added: "By having a national campaign like this we will make people more aware, but I am concerned that we do not really have the key staff in place, such as exercise advisors and dietitians, to make a real difference."
But Betty McBride, Director of Policy and Communications at the British Heart Foundation, said: "We urge people to grab this check-up with both hands if it comes their way. Don't let the first time you realise you have heart disease be at the start of a 999 call."
The British Lung Foundation expressed disappointment that respiratory checks will not form part of the new programme.
Dame Helena Shovelton, BLF chief executive, said: "Respiratory disease is the UK's second biggest killer and one of the biggest diseases of inequality, yet it has been spectacularly overlooked in this announcement."
Next week will also see the launch of MRSA screening in hospitals for most patients undergoing non-emergency surgery - only those undergoing simple procedures such as some mole removals will not be screened.
Free prescriptions for cancer patients are also becoming available.