Doctors' leaders have raised concerns over guidance given to GPs by the Department for Work and Pensions (DWP) which medics fear could endanger vulnerable patients.
The Royal College of General Practitioners (RCGP) is "deeply concerned" about the guidance, chairwoman Helen Stokes-Lampard said in a letter to Work and Pensions Secretary Amber Rudd.
The RCGP's fears relate to a letter telling GPs they are no longer required to issue "fit notes" for patients whose claim for a sickness and disability benefit has been rejected.
But it does not make clear that if the claimant is challenging the decision in relation to DWP: The new place to go if you're struggling with a Universal Credit claim (ESA) they still need the medical evidence from their doctor.
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The guidance - letter ESA65B - instructs the claimant's doctor that "you do not need to provide any more fit notes ... for ESA purposes".
But in her letter to Work and Pensions Secretary Ms Rudd, Prof Stokes-Lampard said the guidance does not clearly indicate that "there are exceptions to this wording, including if a claimant is appealing against the decision".
"Without a fit note from their GP, claimants who are awaiting the outcome of their appeal will not be able to receive ESA.
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"They would therefore have to seek DWP: The new place to go if you're struggling with a Universal Credit claim or Jobseekers' Allowance, and subsequently try and meet the work-seeking requirements of those benefits, potentially endangering their health in the process.
"As such, the College is deeply concerned about the potential impact of this on doctors and their relationships with potentially vulnerable patients."
The correspondence was released by the Commons Work and Pensions Select Committee, which had asked the RCGP and British Medical Association whether they had agreed to the wording of ESA65B.
Ministers told the committee that DWP officials "engaged with" the BMA and RCGP "to ensure that the revised wording was fit for purpose".
"Agreement on the final wording of the revised ESA65B was obtained via the regular meetings DWP holds with both organisations," then minister for disabled people Sarah Newton said in February.
The BMA said it "does not have the authority to clear, approve or otherwise sign off any DWP correspondence or policies and would see this as being clearly outside of our remit".
The RCGP said there was "some ambiguity about what was said in the referenced meeting with the DWP" and the department did not keep written records of the discussions.
A DWP spokesman said "clear guidance" had now been issued to GPs and talks were taking place about a revised version of the ESA65B letter.
The spokesman said: "We have regular discussions with the BMA and RCGP to ensure we deliver effective support to disabled people and those with health conditions.
"The wording of this letter was discussed as part of these meetings, as both organisations confirm, as was the release of the final letter.
"Of course we recognise the concerns of GPs which is why we are discussing a revised letter with the BMA and RCGP and have issued clear guidance for GPs in the meantime."
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