The £6.2bn upgrade of the NHS IT system in England is set to come under criticism from finance watchdogs.
GPs have concerns about some parts of the new system
The National Audit Office report, due to be published on Friday, examines whether it is getting value for money and what progress has been made so far.
The project has been dogged by delays and surveys showing it does not have the confidence of doctors and patients.
But ministers said there had been teething problems with the 10-year project, but it was on the right track.
KEY PARTS OF NHS IT UPGRADE
Choose and book - A system to allow patients to book hospital appointments at a place, date and time of their convenience from GP surgeries. Nearly 10m such referrals are made each year
NHS care records service - An electronic database of patient medical records which will allow NHS staff across the country to access information wherever someone is treated
Electronic prescriptions - More than 325m prescriptions are made each year. By 2007 the paper based system will be replaced with an electronic version, which will allow patients to pick up repeat prescriptions from any pharmacy in the country
The programme, run by a government agency called Connecting for Health, is aimed at linking more than 30,000 GPs to nearly 300 hospitals by 2012.
In total it could cost up to £20bn, but some of this will go on maintenance and training that would have been spent anyway.
It involves an online booking system, a centralised medical records system for 50m patients, e-prescriptions and fast computer network links between NHS organisations.
The online booking system Choose and Book is already a year behind schedule, while the electronic records system has been delayed by more than two years.
Fears have also been raised about patient confidentiality as the electronic records system will allow health professionals anywhere in the NHS to access an individual's medical records.
The government is planning to restrict access.
Richard Vautrey, the IT lead on the British Medical Association's GPs committee, said the introduction of the system was "stuttering".
He added: "We still have serious concerns about patient confidentiality.
"But it is just one of many problems. IT systems on this scale are always going to run into problems.
"But the problem is that politicians have raised the public's expectations by insisting on an unrealistic timetable."
And in a poll of nearly 800 doctors by the BBC last month, two-thirds said the IT upgrade was not a good use of NHS resources.
Tony Collins, of Computer Weekly magazine said the job of introducing an NHS-wide IT system was simply bigger than the government expected.
"The NHS comprises hundreds of businesses, and it was more complicated, more time-consuming and more expensive than they thought."
Nigel Edwards, policy director of the NHS Confederation, told BBC News the project was in fact "largely on budget", with the predicted cost around £6.2bn - but that there was an extra £18bn on top of that which had always been anticipated for annual IT running costs.
"This impression of an absolutely eye-wateringly large overspend is probably slightly incorrect.
"There's a degree of anxiety because, while the procurement was done really rather well, not enough attention was paid initially to really involving frontline clinical staff in finding out what they wanted and bringing them along with the programme."
Ahead of publication of the NAO report, Health Minister Lord Warner moved to reassure the public the government had got to grips with the scheme.
He announced a date would be set next year for the start of the piloting of the electronic records system, while a taskforce would be set up to speed up delivery of the system.
He said parts of the scheme had experienced "teething problems", but urged doctors to work with the government to ensure the system got up-and-running.
"We cannot carry on with the cumbersome, outdated and I would say sometimes dangerous paper-based system."