Hospitals must deliver the same standard of care to patients seven days a week or face huge fines, NHS England's medical director has announced.
Sir Bruce Keogh said he wants to scrap the "historic" practice of relying on junior doctors at weekends without consultants being present.
It follows the end of a major review of seven-day services amid concerns over higher death rates for patients treated on Saturdays or Sundays.
Speaking ahead of the report's publication today, he told The Sunday Times that hospital trusts will be contractually-bound to run a full service seven days a week - with breaches costing them up to 2.5% of their annual income of up to £500 million.
Hospitals that refuse or fail to provide safe weekend care could also face loosing their right to use junior doctors - a prospect he said fills hospitals with "horror".
He told the newspaper that a seven-day NHS would "undo more than 50 years of accumulated custom and practice which have failed to put the interests of patients first".
Within three years all patients admitted to a hospital ward as an emergency will see a consultant within 14 hours, and those already in hospital will be reviewed by one every 24 hours.
Routine surgery will also be available for minor conditions, such as hernias, as well as blood tests, heart checks and biopsies, saving patients from having to take time off work.
Services such as X-rays, ultrasounds, CT and MRI scans will be carried out promptly at weekends, following the review.
"Two things are key to this," he said. "One is the availability of diagnostic tests at the weekend, because the key to treating somebody is a diagnosis.
"Then you need someone experienced to interpret those tests and to institute the right treatment.
"People are still kept waiting at the weekend for a diagnosis. We have a system that is not built around the convenience of patients and is not compassionate to patients for part of the week."
The changes will cost about 2% of the NHS's operating budget of £97 billion, he added.
He dismissed criticisms that it could cost much more - arguing that theatres, consulting rooms and recovery wards left empty over the weekend are inefficient and a seven-day service could mean fewer resources are required.
NHS England declined to comment on the review ahead of its publication.
The announcement comes as a group of senior consultants called for proper staffing of NHS wards at weekends.
In an open letter published in The Telegraph last week, eight surgeons raised concerns that patients were being put at risk because inexperienced hospital staff were being forced to take on too much responsibility.
It follows the treatment given to one of the consultants, retired surgeon Russell Hopkins, whose after-care following a hip operation in June 2011 failed him "catastrophically", the surgeons wrote.
Mr Hopkins, a former Wales British Medical Association chairman, was left with nerve and bladder damage after being left for days without seeing a consultant as his condition worsened, the Telegraph reported.
"The NHS is repaying a lifetime of service with negligence and long-term disability," the surgeons wrote.
"We, the other signatories, are experienced consultants who share his analysis of how the system failed him and why it fails so many others.
"Surgery is too large and technical for a shift system of junior staff."
Dean Royles, chief executive of the NHS Employers organisation, said: "Seven-day working is probably the most important issue facing the NHS at the current time, and movement in this direction is essential if we are to ensure its sustainable long-term future.
"The NHS can't afford to sit back and rest on the laurels of its 65-year history."
A British Medical Association (BMA) spokeswoman said: "The BMA has been clear in its support for consistently high quality patient care being delivered seven days a week. Doctors firmly believe that patient outcome should not be affected by what day of the week they fall ill.
But she said it is a "complicated problem which will not be easily resolved by one single 'quick fix'".
Shadow health secretary Andy Burnham said the Government must set out how Sir Bruce's recommendations would be paid for.
He said: "This idea is right in principle but, with the NHS in increasing financial distress, the Government must set out clearly how it will be paid for."
Health Secretary Jeremy Hunt said: "Patients should be at the heart of the NHS and be able to depend on it every day - not just Monday to Friday.
"I want the NHS to expand to provide seven-day services so that more patients get the right care, when they need it. It is great news that Sir Bruce Keogh will be setting out his plans for the NHS to provide seven-day services."