In an interview with BBC Radio 4's Today programme, Mr Johnson criticised practices that close on Wednesday or Thursday afternoons, and said patients should be able to visit GPs after work.
'We need to address that,' he said. Mr Johnson added that some practices were improving access by opening on Saturday mornings, and called for this to become more widespread.
GPC chairman Dr Laurence Buckman said that if practices offered routine surgeries over extended hours, other NHS services such as laboratories, hospital outpatient departments and X-ray facilities would need to stay open in tandem. Practices would need additional funding to pay staff for longer hours, he added.
'This will cost a lot of money, never mind the fact that there might not be enough GPs and other NHS staff to a provide such a service,' Dr Buckman said.
'The government introduced the new contract and now seems to be trying to destroy its agreement only three years later.'
Dr Buckman said that, if practices had to open later they may sacrifice some daytime surgeries.
'The public must ask if these opening hours would be a good use of NHS resources when it is something only a small number of patients want,' he said.
He added that practices never provided routine Saturday-morning care, but opened for emergencies.
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