The warning comes as GPs in north-west England launched extended hours pilots, and as NHS England's Seven-Day Services Programme met patient groups.
More than 30 patient and carer organisations met NHS leaders at an event run by NHS England medical director Professor Sir Bruce Keogh's Seven Days programme.
One organiser, director of national improvement programmes at NHS Improving Quality Dr Janet Williamson, told GP patients wanted more convenient access to integrated services.
'Patients want to see much stronger working between primary and secondary care, and a whole system approach,' she said.
Among issues raised by patients was whether GPs were a 'barrier to seven-day services'.
In north-west England, GPs are driving the launch of a seven-day access pilot programme.
Proposals by GP groups in Greater Manchester to develop integrated care models have been awarded funding worth around £2m by the local NHS England area team.
One winning bid, by GPs in Middleton, in Rochdale, will extend opening hours until 9.30pm on Monday to Friday and offer weekend GP access. GP Dr Mohammed Jiva, who leads the £500,000 scheme, said patients denied access to GPs 'are ending up at A&E, costing local commissioners a lot of money that should be invested in primary care'.
The six-month pilot would see one practice in the town open for the extended hours. 'There is some concern about GPs being cornered into doing this as part of our core work,' said Dr Jiva. 'But this is new money.'
If it kept patients out of A&E, savings could pay for the service to continue, he said. But Manchester LMC honorary secretary Dr John Hughes, criticised the programme, condemning some GPs involved as 'zealots' looking to 'make a quick buck'.
Dr Jiva rejected the charge, arguing his group aimed to improve general practice and had worked for free on the bid.
Dr Hughes said there was a lack of capacity to support seven-day services and that GPs offering evening and weekend cover would limit availability in normal hours and could divert funding from other services.
GPC deputy chairman Dr Richard Vautrey warned that funding of daytime general practice and unsustainable workloads must be prioritised.