Forcing GPs to work on Sundays would be "irrational, nonsensical and downright bizarre", according to the the chairwoman of the Royal College of GPs.
Dr Maureen Baker is set to rubbish Government plans to introduce seven-day GP services where patients do not want or need it when she speaks at a conference on Saturday.
She will claim that general practice is at a "crossroads" and insist on changes in policy, including greater funding, to ensure that GP services do not crumble and form a "threat to the sustainability of the whole NHS".
"We know from the evaluation of the Challenge Fund that in many areas there isn't a strong appetite for access to routine services on Sundays, and it would be irrational, nonsensical and downright bizarre for the Government to force this on GPs regardless of actual need," Dr Baker is expected to say.
She will speak at a one-day Local Medical Committees conference on GP services in London hosted by the British Medical Association.
In her speech she is set to compare the state of GP services to a moment from Lord Of The Rings when Sam and Frodo have to travel through Mordor to get to Mount Doom.
She will say: "Yes, that may sound a bit dramatic things really can feel that bad sometimes - like you're carrying a heavy burden through an unforgiving landscape, with all hope for the future rapidly draining away."
After highlighting what she calls a "scandalous decline" in general practice funding as a proportion of the NHS budget - down from nearly 11% 10 years ago to just 8.3% today - she will call for more GPs to be recruited and retained.
To tackle a potential "deepening crisis", she will recommend "an emergency package of measures, backed with funding, to save general practice from the brink," that will include special "resilience teams" to plug staffing gaps and investment in out-of-hours services.
She is also due to call for an overhaul of the inspection regime currently in place which she will describe as "heavy handed, bureaucratic and frankly soul-destroying".