NHS England said that an estimated nine million extra appointments per year are now available to patients outside of normal working hours.
The extended access available from today means people will be able to see a doctor, nurse or other member of a practice team during evenings and weekends.
NHS England said the service has arrived three months ahead of schedule and will help ease pressure on the health service during the winter period.
A recent investigation revealed, however, that more than one in four GP appointments were left unused at weekends in pilot areas where the extended hours were available.
Family doctors said the findings by Pulse Magazine showed that the policy, at a time of growing GP shortages, was a “ridiculous luxury”.
At least £3.5 billion more in real terms will be invested in primary medical and community services, which will also improve access to weekday "in hours" services, NHS England said.
The health commissioning body said there are 5,321 more primary health professionals working in primary care than three years ago - higher than its target of an additional 5,000 by 2020.
Professor Helen Stokes-Lampard, chair of the Royal College of GPs, said: "GPs across the country are going above and beyond to ensure we can deliver good, safe care for our patients under intense resource and workforce pressures.
"All practices in England now offer some form of extended access to routine GP services, and they will have tailored these to the needs of their local population."
She said that doctors were preparing for a "very busy winter" in general practice.
"Our patients should always be able to access GP services if they become ill, either through our routine service, or the GP out of hours service," she said.
"But we would also encourage patients to think about whether they really need to see a GP, or whether self-care or visiting a pharmacist are options in the first instance."
NHS England said extended appointment times proved popular during trials, including in Herefordshire where more than nine in 10 appointments were used by patients in August.
In London, where the services have existed for 18 months, almost three quarters of appointments are taken up.
Extended appointments will be available through designated local NHS services and in some cases a patient's own GP practice.
Evening and weekend appointments will be offered in addition to other services such as out of hours GPs and NHS 111 that offer access to clinicians at any time, day or night.
Dominic Hardy, NHS England's director of primary care delivery, said: "Strengthening general practice is an important part of the NHS long-term plan and local health services have worked hard to ensure patients have access to our excellent general practice services right across the country.
"Because of this hard work, we have been able to make these extra appointments available months ahead of schedule and before winter really starts.
"As well as offering convenience and choice to patients, it will help to reduce some of the pressure on general practice and A&Es, and ease some of the wider system pressures we saw last winter."
Source: Telegraph