Drug firms will prioritise launching medicines in European countries other than the UK after NHS bosses agreed to stall costly treatments, a poll suggests.
A survey of leading pharmaceutical firms also found they think cancer drugs will be hit the most by the changes brought in by National Institute for Health and Care Excellence (Nice) and NHS England.
From today, patients could face delays accessing drugs if they cost £20 million or more in any of the first three years of their rollout across the NHS.
Even when a drug has been approved by Nice - which already has strict rules on affordability - bosses at NHS England can now slow down its delivery to patients for three years or more.
At present, the NHS has 90 days to make Nice-approved drugs available.
NHS England says the scheme means it has more time to negotiate with drug firms to lower the cost of the treatments.
But health charities have objected strongly to the move and say NHS England will also restrict access to certain groups of patients.
The new survey of 32 members of the Association of the British Pharmaceutical Industry (ABPI) found 71% believe their companies will prioritise launching new medicines in European countries over the UK.
Almost nine out of 10 (89%) said they believed the changes will mean a decline in patient access to medicines.
Meanwhile, three-quarters (75%) said they believed the move will impact the introduction of new cancer medicines, with new treatments for immune diseases, genetic conditions, neurological conditions, dementia and heart disease also identified as areas most likely to be affected.
No firm said they thought the changes would increase access to new cost-effective medicines.
The ABPI said that for every 100 patients in France, Spain and Germany put on new drugs in the first year, just 17 patients in the UK currently get access.
ABPI chief executive, Mike Thompson, said: "The day after the NHS announces plans to a deliver a cancer diagnosis in just four weeks, these measures introduce the prospect of a three-year delay for 20% of new cost effective medicines.
"This means thousands of patients who stand to benefit the most, particularly those with cancer, will miss out on the very latest medical breakthroughs.
"The evidence on access to new medicines is overwhelming, patients in England are already getting a bad deal, and as we head towards Brexit we should be catching up with Europe, not introducing measures that mean we'll fall further behind."
Sir Andrew Dillon, chief executive of Nice, said: "There is no predetermined cap on the amount of money the NHS will spend on a new drug.
"The £20 million annual figure is the trigger for a commercial negotiation, not a maximum.
"Only a minority of drugs will be affected by the budget impact test and the number will be further reduced where savings generated by the drug's use will bring its budget impact below £20m.
"For Nice to agree to an NHS England request to extend implementation of a new drug beyond the usual 90 days, a clear case will have to be made including how funding will be made available from the start, to phase in access to treatment."
Emlyn Samuel, Cancer Research UK's senior policy manager, said: "We've made our concerns clear that the introduction of this budget impact test could have a significant effect on cancer patients.
"Any system that potentially delays access to new treatments, once they have been approved by Nice is unacceptable.
"It's important that manufacturers price drugs responsibly, but we don't think this test is necessary.
"There are other options available to the Government which we strongly encourage them to explore."