Eli Lilly, one of the NHS' biggest drug providers, has warned that plans to introduce value-based pricing could delay access to treatment for Alzheimer's, Parkinson's and schizophrenia.
The reforms would mean that companies are paid for drugs according to their innovativeness, effectiveness and benefit to patients.
However, drugs companies have claimed that this could remove the incentive to invest in research for treatments that are not guaranteed to be effective.
"Just by having a price negotiation it could lead to delays in access versus the current approach," said Rick Ascroft, director of corporate affairs at Lilley UK.
"While the goal of the system is to improve access, at least up front it may actually do the opposite."
Proposed NHS reforms will also give GPs greater power to order drugs instead of existing Primary Care Trusts.
Dr Clare Gerada, the new head of the Royal College of GPs, said the reforms could trigger angry reactions from patients.
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