Drugs firms should be required to end their secrecy over clinical trials if they wish to get approval for widespread NHS use of their products, the Commons health select committee said last night.

The MPs demanded that commercially confidential information be revealed when treatments were assessed for cost effectiveness by Nice, the national institute for clinical excellence.

The move could revolutionise the way the pharmaceutical industry operates, but the committee said the change was needed to improve public credibility in the system by which the NHS determines which treatments are funded.

The health committee's investigations into Nice, the government body committed to ending "postcode prescribing", revealed widespread concern that it had not published the evidence on which it based its appraisals. The MPs said all information used in Nice's decisions should be available for scrutiny.

"If industry or others have previously unpublished data which they want to use to support their case, then this must no longer be presented to Nice subject to confidentiality."

Any company demanding continued secrecy should risk its treatment not being appraised, said the committee. Drugs firms would be unlikely to opt out, since refusal to allow access to evidence would be likely to have a "negative effect" on public confidence in their products.

Nice also had a huge backlog of work - trying to catch up with drugs that have been approved for sale for years without being assessed as to whether they are worth expenditure by the NHS.