More than three quarters of Britain's 117 leading medical research charities expect the recession to have an impact on their work, according to a survey.
Half said they intended to freeze research funding at the same level as last year, while a quarter planned cut backs.
The Association of Medical Research Charities (AMRC), which carried out the survey, said funding from its members was likely to come under "significant pressure" over the next one or two years.
AMRC charities looking to make cuts estimated reductions of between 10 and 40 per cent.
In the year 2008-2009 members of the umbrella group spent an estimated Ģ936 million on research.
Simon Denegri, the AMRC's chief executive, said: "These are uncertain times for medical research charities. AMRC's survey suggests that while charity funding across the whole spectrum of medical and health research in the UK is being impacted by the downturn, smaller charities funding work into less common conditions are being hit particularly hard. And while their commitment to supporting science in the long-term is undimmed, their ability to weather the short-term will be dependent on an equal commitment from the donating public, Government and their university partners.
"The end-product, such as new treatments, therapies and innovations, will more than repay themselves in the health and well-being of the public."
The AMRC called on the Government to keep investing in science and medical research, maintain the Charity Research Support Fund which helps charities reduce their overheads, introduce tax concessions, and ease the regulatory burden on medical research.