"Outdated" GP services should be overhauled to extend opening hours and be more flexible, business leaders say.
A new GP contract was introduced in 2004
The Confederation of British Industry says businesses lose 38m working hours and £1bn a year because employees have to visit their GP during working hours.
It comes as the government is to meet leading high street companies to discuss increasing access to GP care.
But doctors suggested the CBI hoped to benefit from any privatisation of the health service - a charge it denies.
Access to GP care will be one of the central themes of the NHS review being carried out by Health Minister Lord Darzi.
Lord Darzi, a practising surgeon, is kick-starting the public consultation side of the review on Wednesday with nine citizen juries meeting for the first time.
He will also be hosting a conference in the next few weeks that will look at improving patient access, such as locating GPs in gyms and supermarkets, with companies including Virgin, Boots, Bupa and Lloyds Pharmacy due to attend.
Health Secretary Alan Johnson acknowledged the CBI had a point.
"The days of nine to five and closed at weekends and sometimes closed during the week... has to change.
"We need a health service for the 21st century."
The CBI report said much of the lost time could be avoided if the GP system was more flexible, although it admitted some of this also included GP visits when people were sick and therefore were not a matter of access.
The report said there needed to be a "fundamental rethink" about a service which had changed little since the NHS's foundation in 1948.
It said the investment in the new contract in 2004, which led to a huge hike in salaries while at the same time allowing GPs to give up providing out-of-hours care, had not been matched by improvements in service.
In particular, the CBI called for longer opening hours in areas where there was demand.
Even though a recent government survey of more than 2m patients found more than 80% were satisfied with access, the CBI said there would still be areas where evening and weekend opening was wanted.
The group also said patients should be able to register with more than one GP practice and said pharmacists should be more involved in providing healthy living advice and treating minor ailments such as coughs and colds.
And it added the primary care sector should be opened up more to private providers, pointing out much of the government's NHS reforms have concentrated on hospital care.
Many of these initiatives, with the exception of dual GP registration, are already possible under the current system.
But John Cridland, deputy director general of the CBI, who said the report was not about wanting NHS privatisation, said there was a lack of innovation in primary care.
"Billions of pounds of taxpayers' money is being spent on a GP system which seems unable to respond to patients' needs."
Dr Laurence Buckman, chairman of the BMA's GPs Committee, said GP practice had changed dramatically in recent years with family doctors getting more involved in things such as diabetes and heart care.
"If CBI members think their staff are seeking medical appointments without any real cause, that seems to point to the need for a better occupational health service.
"Is it possible that the CBI is hoping that its members will be able to take part in future privatisation of the health service?"