Patients are being used as a "bargaining chip" by NHS England and the National Institute for Health and Care Excellence (Nice) to drive down the cost of drugs, researchers have warned.
A new plan to delay giving high-cost drugs to patients "may deliver short-term savings but is flawed", they said.
Last week, it emerged patients could face delays of three or more years accessing drugs on the NHS after health bosses agreed the most expensive treatments can be stalled.
Even when a drug has been approved by Nice, bosses at NHS England can now slow down its delivery to patients.
The move applies to any drugs that are expected to cost £20 million or more in any of the first three years of their rollout across the NHS.
At present, the NHS has 90 days to make Nice-approved drugs available.
NHS England says the move will provide more time for negotiations with drug firms to drive down the cost of treatments, but health charities have strongly objected to the move.
In an editorial published in the British Medical Journal (BMJ), experts including Peter Littlejohns, professor of public health at King's College London, and Dr Annette Rid, senior lecturer in bioethics and society at King's, said patients would be excluded from new drugs merely because of how common their disease is.
They used the example of the drug infliximab, which would be handed out to patients with ulcerative colitis but not those with Crohn's disease, which is far more common.
Giving the drug to the Crohn's group would cost far more simply because there are more patients.
They said: "Budget impact is essentially the price per patient multiplied by the number of patients treated. Yet the prevalence of someone's condition should not determine their access to treatment.
"The principle of equity means that like cases should be treated as like; the NHS Constitution requires the NHS to respond to the clinical needs of patients as individuals.
"The new test requires Nice to treat patients in one group less favourably than those in another solely because there are more in the first group than the second. It is numerical discrimination.
"And if large numbers of patients experience delays, the policy threatens widespread harms."
The experts said that perhaps the new policy aims to pressurise drug firms to lower prices when volumes are high.
"But this is to use large patient groups as a bargaining chip.
"Nice's justification for pursuing its approach, that "no alternative solutions" have been put forward, is invalid in our view.
"The recent consultation did not ask for other options. Had it done so, several could have been canvassed."
Sir Andrew Dillon, Nice chief executive, said: "Only a minority of drugs will trigger the budget impact test and fewer still will need a longer period to manage their adoption by the NHS, after the effect of commercial negotiations and the impact on patients have been taken into account.
"We believe these and the other changes that we're now introducing will enhance our ability to optimise access to innovative treatments in the light of the significant financial challenge facing the NHS."
He said funding for the drugs will be phased in from the start. It is unclear how much this would be.