Hundreds of women are being recalled for tests after it was discovered a nurse did not sterilise equipment used for intimate examinations.
The nurse involved has been suspended from the surgery
Up to 500 women were examined at the Perry Street doctors' surgery in Darwen, Lancashire, between 1991 and April this year.
The unsterilised equipment may have left them at risk from diseases including hepatitis B or C and chlamydia.
The nurse has been suspended and is facing disciplinary action.
The GP at the practice Ibrahim Dera is being allowed to continue treating patients - but has been referred to the General Medical Council.
It is believed that she washed the speculums - most commonly used for smear tests - in disinfectant, instead of sterilising them.
The Blackburn with Darwen Primary Care Trust has referred the matter to the General Medical Council.
Vivien Aspey, the trust's chief executive, said that the nurse in question did not realise she was doing anything wrong.
"It wasn't until someone went in from outside - in this case the control of infection nurse from the primary care trust that she realised there was a problem," Ms Aspey said.
She said that the risk of infection was "very low" adding that any women needing treatment would be "fast-tracked".
All the women involved have been notified by letter and will have to undergo blood and urine tests.
A confidential helpline has been set up for any women who may be concerned about their treatment. The number is 01772 904191.