NHS cancer, stroke and cardiac treatment networks have cut staffing by up to a fifth in the last three years, according to the Labour Party.
The party, which obtained the figures under the Freedom of Information Act to the 56 networks in England, claimed the 20% staff cut in cancer networks and 16% in heart and stroke networks is due to funding cuts of up to 25%.
Liz Kendall, shadow minister for care and older people, said: "Ministers have repeatedly promised to protect the funding for clinical networks, yet these figures clearly show this is another in the long list of this government's broken promises on the NHS."
Cancer charity Macmillan Cancer Support said the cuts were "a real concern" and would endanger patient care.
Duleep Allirajah, Head of Policy at Macmillan Cancer Support, said: "This leads to the loss of valuable expertise about cancer services which will put patient care at risk.
"The NHS Commissioning Board has listened to our concerns and some progress has been made. However more needs to be done to safeguard the cancer networks in the NHS shake-up so patients don't suffer."
