The number of NHS nurses and health visitors has fallen since the coalition took power in 2010, despite ministerial pledges to protect the health service's frontline, official figures show.

The number of nurses' posts that have disappeared rose by 700 in June alone and now stands at 5,780 fewer since the general election, according to the latest monthly workforce data released by the NHS's Health and Social Care Information Centre.

The number of health visitors had also fallen by June, despite pledges by the then health secretary Andrew Lansley to hire many more. Some 10,102 were employed by the NHS in England in May 2010 but there are now 9,949.

Labour condemned a government which, it said, "gives tax breaks to millionaires and P45s to nurses". Andy Burnham, the shadow health secretary, said David Cameron had cut the NHS budget two years running despite pledging to protect it and had failed to protect frontline staff. "The result is the NHS frontline is taking a battering from the Tory-led government's mismanagement of the NHS. Over 5,000 nursing jobs have been cut on Cameron's watch, with 700 going in the last month alone," he said.

Lord Howe, the health minister, said 3,500 more doctors and 900 extra midwives had been employed over the same period. "There are always fluctuations in the workforce, and … there are almost 1,000 more clinical staff working in the NHS than there were in May 2010," he said.

In addition, the service now employs some 18,000 fewer administrative staff than in May 2010 and "this is creating savings that will help protect the NHS for future generations", Howe said.