It found that 73% believed the demand for extra hours reflected a patient "want" rather than genuine need.
Only one in four (27%) said they could sympathise with people wanting to fit a GP appointment into a busy schedule.
Nine out of 10 (89%) managers said the money could be better spent on other aspects of patient care, including addressing the needs of the elderly and those with chronic illnesses, developing practice premises and enhancing community services.
One of the managers surveyed said: "After 15 years in practice management, this is perhaps the most naked attempt by the Department of Health to assert political control over GPs, and the justification in terms of patient demand is wafer thin."
Around four in 10 (43%) managers said a single receptionist would be the only nonclinical member of staff present for extended hours in the evening.
Six in 10 (60%) said just one GP would be working at these times.
For the full report of this Management in Practice survey, click here
What are your thoughts about the opening hours debate? Do you agree with the practice managers surveyed? Your comments: (Terms and conditions apply)
"Patients will always demand more of any service that is free. Such service is open to abuse. Our practice has had a Saturday opening for opportunistic screening for smears and immunisations but we were lucky if one person turns up. The NHS should concentrate on patients needs and not patients requirements. Money circulating within the NHS should be put to better use and not for political gains. I for one as a patient of a doctors practice and a full-time working individual would not want my doctor's surgery to be opened at the weekends or later than it is already." - V Henry, London N15
"Our patients are already happy with our opening hours. There is always a surgery over the lunch time and later appts. We are well served with walk-in centres and out-of-hours centres. Our GPs want to know who is going to pay the wages for the rest of the staff as they cannot work alone." - Angela, Wirral