Ministers have said they will push ahead with a plan to put people's medical records on a national electronic database.
However, they have agreed to allow patients to opt out after opposition from doctors and patient groups.
E-care records are part of a wider IT upgrade
What is the government doing?
The electronic patient care records system will allow an individuals medical records, currently held by GPs, to be accessed by NHS staff across the country.
It is part of a 10-year, £6bn upgrade of the health system's IT network, which will also see online bookings and e-prescriptions.
Ministers say the current system, which is predominantly paper-based, is outdated and can lead to unnecessary delays and risks.
One example cited is when ambulance crews are called out to attend to people in their home.
Paramedics say it can often take them a while to find out what medication an individual is on, especially when they are called in the evening and weekends.
What information will be contained on the records?
The pilots, which are starting in the spring, will just contain summary details on the medication an individual may be taking, allergies they have and if they have suffered any adverse reactions to drugs.
The decision on more sensitive data, such as HIV status or whether a woman has had an abortion, will be made later.
There has been suggestions this information could be put in an electronic "sealed envelope", only to be opened in an emergency, however there are concerns over whether this is actually possible.
Why has it proved controversial?
The major criticism is that it risks patient confidentiality.
Doctors and patient groups have argued that by putting sensitive details on a national database the information could be abused and even fall into the hands of insurance companies and employers.
A poll of over 1,000 GPs by the Guardian newspaper last month found half would consider refusing to put patients records automatically on the database.
Many said they doubted the security of the new system.
The Patients Association have warned one consequence will be that patients may become reluctant to tell their GPs about sensitive information, harming the doctor/patient relationship.
How will the veto work?
Before the data is put on the national database, patients will be able to view it online through as system called HealthSpace.
They will be entitled to amend the data and even refuse to have it on the national database.
If patients do not view their data, it will be assumed they are consenting.
But patients will also be able to block the "uploading" of the data at an earlier stage.
Under the Data Protection Act, they can refuse to have any medical information held on a computer at all by arguing it will cause them mental distress.
Will this appease critics?
The doctors trade union, the British Medical Association, which sat on the taskforce which came up with the veto, has called it a good first step.
But in many ways the government has just delayed the trickiest question - what to do with more sensitive data?
At the moment, the e-record is just a summary record containing basic details.
But paper records actually contain information on all sorts of things, including HIV status and abortion history.
There has been suggestions this could be put in a "sealed envelope", only to be opened in an emergency.
However, security experts have questioned just how secure this may be and whether it will work properly.
Leading computer scientists recently wrote to the Health Select Committee spelling out their concerns.
And the fact remains that many people are uncomfortable about having such information stored on a national database.
Some fear that the data could be sold on to outside parties, such as employers and insurance companies, with an interest in personal details.