The Department of Health is axing 1,700 doctors, nurses and other health professionals who work on programmes concerning every aspect of NHS care.

The specialists were recruited from the NHS to work with civil servants because of their expertise. They include dentists, dieticians, psychologists, psychiatrists, consultants, nutritionists and experts in tackling public health problems.

Those being made redundant work at DoH buildings in London and at offices around England. They work to combat diseases, improve patient care, reduce the burden on the NHS from problems such as alcohol and obesity, and include some of those working on the government's drive to use the Olympics to encourage more people to be more physically active.

The DoH has not announced the move and has refused to answer questions about it from the Guardian. But staff affected were told in letters in June that they were being placed at risk of redundancy as a direct result of health secretary Andrew Lansley's huge shakeup of the NHS and public health. The letters say: "There are changes in the priorities for the Department of Health; this is because of the new government's agenda, and the funding needed for reinvestment in the NHS."

Human resources staff have said a total of 2,000 people are affected. They are all paid out of "programme funding" – budgets to fund particular areas of work which the government has decided to abolish by March 2011.

Only 300 of the 2,000 are guaranteed security of employment because they are civil servants temporarily working on specific programmes. DoH sources say that as some of the 1,700 are finding new jobs, around 1,500 are expected to see their posts disappear. The 1,700 represent about 40% of the DoH's 4,286 staff.

A March 2010 document available on the DoH's intranet says there will be "a reduction in programme-funded workers to zero in line with 2010-11 budget and business plans". It adds: "There are circa 300 civil servants funded from programme budgets … There are circa 1,700 non-civil servants funded through programme budgets."

At recent meetings, officials have made clear that everyone who is programme-funded will have no work beyond the end of March at the latest. Some have already been laid off. It is finalising details of redundancy packages.

The move is designed, the DoH says, to free up more money for direct patient care. But senior doctors are worried that it will deprive the ministry of vital expertise at a time when the NHS is set to undergo its biggest overhaul since its inception in 1948, and pressure to improve prevention and quality of care is intense due to the NHS's need to save £20bn by 2014.

Prof Lindsey Davies, president of the Faculty of Public Health, said: "Public health teams around the country have a crucial role in making sure we and our children can live healthier lives, now and in the future. The government clearly wants to commit to tackling some of the biggest killers such as obesity, smoking and heart disease. That's great – so why cut funds for public health workers? These people are working hard to make a real difference. Losing them now, when there's so much more to be done, just doesn't make sense."

Most have spent years working for primary care trusts, hospitals, medical charities or in medical academia before accepting an offer to bring their specialist knowledge into the DoH. Some have worked at the ministry for seven years.

Unison is in talks with the NHS about 294 staff who were due to lose their jobs. Dave Prentis, Unison's general secretary, said: "The government says that it is protecting the NHS frontline, but these medical experts are on the frontline of prevention. It makes no sense to get rid of the wide-ranging expertise that these specialists bring to the Department of Health and the vital role they play in helping to prevent diseases. Losing these jobs will cut the heart out of vital prevention work. It is far cheaper to keep people healthy and out of hospital than to treat them in it."

A department spokeswoman said: "Some of these were temporary programmes that were coming to an end anyway. We are reshaping and improving public health strategies. There will be plenty of opportunities and jobs to be done in both national and locally-led public health services." She said the government "was committed to increasing the health budget in each year of this parliament. We will spend that money wisely, including the prioritisation public health and preventative work."