The outsourcing of NHS England back office tasks to a private company was a "shambles" according to MPs.
The report by the the Public Accounts Committee (PAC) says it meant thousands of GPs, dentists and opticians had been delayed in treating patients.
It added that the contract with outsourcing company Capita "potentially... put patients at risk of serious harm".
It said Capita had failed to deliver on key aspects of its service contract.
Capita said the contract was over its initial teething problems, while NHS England said the arrangement was saving money that was being used in frontline health services.
Cervical screening blunder
Capita signed a seven year contract in 2015 to perform back-office tasks for NHS England.
The PAC report said that once initial problems came to light, not enough was done to stop the issues getting worse.
It described how delays in moving medical records from one practice to another meant patients may not have been able to access necessary care.
Some 87 women were incorrectly notified that they were no longer part of the cervical screening programme.
The report also said doctors had reported problems with the transfer of medical documents, and problems caused by shortages of stock in the NHS supply chain.
"A complete mess"
PAC chairwoman Meg Hillier said: "NHS England made a complete mess of what could have been a responsible measure to save taxpayers' money.
"It is clearly unacceptable that poor procurement should put patients at risk of harm and undermine the ability of GPs, dentists, opticians and pharmacists to do their jobs."
The contract with Capita was intended to reduce primary care support service costs by 35%, and modernise the service.
The services outsourced included:
- organising payments to GP practices, opticians and pharmacies
- administering the GPs' pensions
- confirming GPs', dentists' and opticians' qualifications
- sending out letters for those eligible for cervical screening
The PAC report said neither party understood the services that were being contracted.
In May the National Audit Office also issued a report on Capita's performance, saying services had been "way below" acceptable standards, although no harm to patients had been found.
A Capita spokesman the firm had "apologised for unacceptable failings in relation to the initial delivery of this contract".
It added: "We are now meeting the vast majority of key performance targets, and have put in place a new governance arrangement with NHS England to ensure improvement continues."
An NHS England spokesman said: "We will continue to work with medical professionals and Capita to resolve the historic issues which this look-back report reviews.
"But by making this change over the past two years, the NHS has successfully saved taxpayers £60 million, which has been successfully reinvested in frontline NHS patient care, funding the equivalent of an extra 30,000 operations."