A survey showed 77% of the charities fear the downturn will significantly affect their work, the Association of Medical Research Charities (AMRC) said.

Some plan to reduce their research spending by between 10% and 40% to help them cope, found the AMRC, which represents 117 health organisations.

The smaller charities, including those conducting research into less common illnesses, are particularly badly hit.

The AMRC urged government ministers to extend the life of the charity research support fund, which helps cover the cost of the infrastructure at universities and hospitals needed to support research projects.

The government puts £195m a year into it, but the scheme is due to expire in 2011.

In addition, charities want changes to the VAT and gift aid rules, lighter regulation of clinical trials, and a pledge to maintain scientific and medical research funding.