More than half of practices in England have had no investment in premises for more than a decade, the poll found.
GPC chairman Dr Chaand Nagpaul said buildings in some areas were in such poor condition they are undermining patient care.
GP leaders are pressing for urgent government action, with GPC members set to meet health minister Earl Howe, along with DH and NHS Property Services officials on Thursday to discuss GP premises.
What the BMA poll found:
40% of practices feel that their current facilities are not adequate to deliver services.
Almost 70% of GPs feel their facilities are too small to deliver extra or additional services.
Almost 60% of GPs have to share consulting rooms or employ 'hotdesking'.
Over 40% of practices say hotdesking restricts the number of appointments they can provide; almost a third said it damages overall delivery of services.
Over half of practices have seen no investment or refurbishment in the past 10 years.
60% of GPs think their practice is not big enough to provide vital training and education.
Northamptonshire GP Dr Gareth Williams said his 10,000-patient practice had just six car parking spaces and poor disabled access, with half of its consultation rooms unreachable to some disabled patients.
‘Our surgery is full to bursting, with the practice manager and secretary working out of a portakabin, but our patient list is still increasing. This means that our patients are waiting unnecessarily for an appointment and are quite rightly frustrated at the delay getting the treatment they need,’ he said.
GPC call for premises investment
The GPC will argue at today's summit for new premises investment as well as policies to support improvements, such as lease clauses with breaks, flexibilities around planning permission and support with loans.
The state of premises also undermines government and NHS priorities to move care out of hospitals, GP leaders have said.
‘With the drive from ministers to move services into the community and out of hospitals, it is particularly worrying that seven out of 10 GP practices are being held back from offering additional or enhanced services,' said Dr Nagpaul.
GPC premises lead Dr Peter Holden told GP he thinks the government is listening.
Limiting factor for practices
‘People realise premises are one of the biggest limiting factors in moving care out of hospital, but also in delivering care for patients,' he said.
‘This is really bringing it to an absolute focus – we need to start talking about surgeries.’
Dr Holden said most practices ‘don’t need a large, £5m ribbon-cutting opportunity’.
‘Most need between £300,000 and 500,000 and a few extra rooms,’ he said.
The summit, he added, was a chance to ‘stop the ping pong’ between NHS organisations over who was responsible for securing improvements to GP premises.