British cancer patients are being denied life-saving drugs and trials of revolutionary treatments are being derailed by the red tape and extra costs brought on by Brexit, a leaked report warns.

Soaring numbers are being diagnosed with the disease amid a growing and ageing population, improved diagnosis initiatives and wider public awareness – making global collaborations to find new medicines essential.

But five years after the UK’s exit from the EU, the most comprehensive analysis of its kind concludes that while patients across Europe are benefiting from a golden age of pioneering research and novel treatments, Britons with cancer have “lost out” thanks to rising prices and red tape.

Brexit has “damaged the practical ability” of doctors to offer NHS patients life-saving new drugs via international clinical trials, according to the 54-page report obtained by the Guardian.

In some cases, the cost of importing new cancer drugs for Britons has nearly quadrupled as a result of post-Brexit red tape. Some trials have had shipping costs alone increase to 10 times since Brexit.

The extra rules and costs have had a “significant negative impact” on UK cancer research, creating “new barriers” that are “holding back life-saving research” for Britons, the report says.

In some cases, the impact has been devastating. Children are among the NHS cancer patients whose tumours have returned or treatment has stopped working, leaving them in limbo and denied drugs that could extend or save their lives, senior doctors told the Guardian.

Sources said officials in the Cabinet Office and the Department for Science, Innovation and Technology were studying the findings of the review.

It cites evidence from a range of leading clinicians, scientists and researchers, and was compiled by experts from organisations including Cancer Research UK, the University of Southampton, and Hatch, a research consultancy.

In a statement, the government said clinical trials were vital to millions of Britons with long-term conditions for whom limited treatments were available in routine care, including cancer patients for whom routine therapies were ineffective.

Ministers were committed to “strengthening” the UK’s relationship with the EU on research, and the government offered “extensive support” for UK researchers to help them secure funding, a spokesperson added.

Three areas of UK cancer research have been hit particularly hard by its departure from the EU, according to the report. They are the regulatory environment for clinical trials, the mobility of the cancer research workforce and access to research funding and collaboration.

Clinical trial groups and universities are struggling to attract “global talent” in cancer research to come to Britain, with UK patients missing out on the expertise of the world’s top cancer scientists.

At the same time, UK researchers are finding it “more difficult” to attract grant funding to explore new ways to save the lives of patients “due to additional bureaucracy since the UK left the EU”.

The report also reveals the UK is needlessly duplicating drug testing in clinical trials involving the UK and EU, with extra checks causing potentially deadly delays.

In one case, the UK had to spend an extra £22,000 for an official to certify batches of aspirin for use in a cancer trial. Aspirin is one of the world’s most familiar drugs and the batches had already been checked in the EU.

Meanwhile, Brexit is having a wider, damaging effect on life-saving research in the EU, the report adds. “The exclusion of UK researchers from European cancer research activities has had, and will continue to have, negative consequences for the overall European cancer research effort,” it says.

Leading experts shown the report by the Guardian said the harm Brexit had inflicted on UK cancer research and NHS patients had been inevitable and predicted to occur.

“Those of us who understood the EU warned repeatedly about precisely these concerns,” said Dr Martin McKee, a professor of European Public Health at the London School of Hygiene & Tropical Medicine. “These findings are not just predictable, they were predicted.”

He added: “It was always inevitable that Brexit would lead to costly duplication and barriers to collaboration.”

Mark Dayan, the Brexit programme lead at the Nuffield Trust, a health thinktank, said the report highlighted “concrete examples” of “disruptions which many warned were inevitable from the moment that we left the EU with a relatively hard Brexit for health and research”.

The UK and EU are due to renew the trade and cooperation agreement this year, and discuss a wider reset which will shape the future UK-EU relationship.

Keir Starmer should make the case for “a new pact to protect health”, Dayan said, “cutting back pointless post-Brexit red tape on medicines testing and research approvals by being willing to cooperate and offer guarantees”.

The report recommends the creation of a mutual recognition agreement for testing medicines, to cut costs for researchers leading cross-border trials. Without it, patients will experience further delays to trials in future, denying them access to potentially life-saving treatments, it says.

A government spokesperson said: “We are strengthening our relationship with the EU on research and have been providing extensive support for researchers to help them secure funding from the £80bn Horizon Europe programme and get more vital treatments from the lab to patients.”

Last year, the Guardian revealed how hundreds of thousands of people in the UK were being forced to wait months to begin even basic cancer treatment, such as surgery, radiotherapy or chemotherapy, with deadly delays “routine” and even children denied timely care.