Another 3,591 women were not sent information on cervical screening as a result of errors by Capita, NHS England has said.

Last month, it emerged that 47,708 women did not receive a smear test invitation, reminder or results between January and June because of Capita’s failure to send out letters.

On Wednesday, NHSE said the number had risen to more than 50,000 after a review uncovered more correspondence from last year that was not sent.

Capita said about half of the newly identified cases related to test results, but only a small proportion were abnormal result letters. It said those women had received a referral and there was no evidence of any harm resulting from its mistake.

The private contractor, which is responsible for GP back-office services as part of a seven-year £330m contract, said a senior executive responsible for the contract had left the company. But the Royal College of GPs (RCGP) said Capita had lost the trust of NHS workers.

Facebook Twitter Pinterest Helen Stokes-Lampard: ‘This is simply not good enough.’ Photograph: Sam Friedrich/Guardian

Helen Stokes-Lampard, the RCGP chair, said: “This is simply not good enough. Less than a month since we initially heard about this cervical screening error, we are now hearing it is more serious, and has affected thousands more women.

“Capita has been shown time and time again to be unable to deliver on the work it has been contracted to do in the NHS. This is completely unacceptable – people working throughout the NHS have lost all confidence in Capita, and it really is time for NHS England to reconsider its contract with them.”

She said the error would also damage women’s confidence in the programme at a time when the takeup of testing, particularly among younger women, was falling. However, she advised women not to panic. Capita said all those involved were written to on Tuesday advising them what to do. It apologised to all those affected.

Dr Richard Vautrey, the BMA GP committee chair, repeated the doctors’ union’s demand for the contractor to be stripped of its contract. “This is just the latest in a long line of failures since Capita took over a number of GP services in 2015, and yet NHS England have not demonstrated to the profession that they are serious at addressing what ultimately they are responsible for,” he said.

About 3,000 women a year are diagnosed with cervical cancer, which kills about 850 a year. Women aged between 25 and 49 who are registered with a GP receive an invitation to screening every three or five years.