Around 7,000 more women in the UK have received potentially faulty PIP breast implants than previously thought, the Government announced today.
Around 47,000 British women in total are now believed to have been given the implants manufactured by closed French company Poly Implant Prothese (PIP).
The implants were filled with non-medical grade silicone intended for use in mattresses and have been linked to rupture and swelling in the body.
French authorities previously advised that only PIP implants that were used after 2001 may have included the unauthorised gel.
But following an investigation by the UK regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), French authorities said this week that PIP implants made before 2001 may also contain the unauthorised silicone.
This could bring the total number of women affected by the scandal in the UK to around 47,000, including those affected before and after 2001.
According to the Department of Health, around one in five breast implants need replacing within 10 years, regardless of their make, and it says it is unlikely that all 7,000 extra women still have the implants in place.
In January the Government announced that anxious women given PIP breast implants on the NHS would be able to have them removed for free, with private firms expected to offer the same deal.
However, it said any woman refused help by a private company would be able to visit their GP and access NHS care.
This deal will now apply to any woman affected by today's update.
Health Secretary Andrew Lansley said: "The French regulator has confirmed this week that more women may be affected by the criminal activity of the French breast implant manufacturer PIP.
"These women are the victims of a fraudulent company and I know this situation is causing a huge amount of anxiety. I want to reassure those affected by the news today that they will be provided with all the help they need from the NHS.
"We are still working to get private clinics to live up to their responsibilities and look after their patients.
"Our commitment is to ensure support for all women from the NHS if needed; we will continue to press for the same standard of care or redress from private providers."
The vast majority of operations involving PIP implants were carried out in private clinics, including those run by Transform and the Harley Medical Group.
Earlier this year MHRA experts concluded there was no evidence to recommend routine removal of the implants. However, they said they could not entirely rule out that some were toxic.
As of the end of last week GPs had referred 4,534 patients for NHS care who received their PIP implants in private clinics.
Overall, 2,170 scans have been completed on these patients and 224 patients have decided to have their implants removed, with 51 operations performed to date.
Of those given breast surgery on the NHS, such as breast reconstruction following cancer, a total of 725 women have been contacted to date.
Some 34 scans have been completed among this group and 98 women have opted to have their implants removed, with 12 operations already having taken place.
Women are urged to find out if they have PIP implants and speak to their GP or surgeon if they are concerned.
Chief medical officer Professor Dame Sally Davies said: "The expert group advises that there is no evidence to suggest that every woman with a PIP implant should have them removed. But we know this is a worrying time for them and want them to be able to see a GP or specialist to get reassurance and have them removed if necessary.
"All women who had the implants put in on the NHS will be able to have them removed and replaced by the NHS. We expect private clinics to offer their patients the same care. If they refuse, the NHS will provide advice, a scan and, if necessary, remove the implants.
"Private patients will not however be able to have their implants replaced on the NHS unless this is clinically necessary.
"We will be placing adverts in the weekend papers again to inform all women with PIP implants about the advice from the experts and how they can get help if they are concerned.
"I have also written to GPs today to remind them that we want them to help women with PIP implants."
In France, the government told 30,000 women they should have the implants removed while the Czech and German authorities have also recommended that women should also have them taken out.
Nigel Mercer, from the British Association of Aesthetic Plastic Surgeons (BAAPS), said the UK may never know the true number of women who received PIP implants.
"It now looks as though the timebomb has completely exploded - I don't think we will definitely have caught all the women," he said.
"We know of some patients who do not know what implants they have got in and they have been unable to find out.
"Either the clinic has gone bust or the women were not told at the time of the original operation what was being put in.
"We may never completely know who does have them in or who doesn't - patient records only have to be kept my law for seven years."
He added: "The advice for women following today's announcement is as before - if you have a breast implant and you're not sure what you've got, ask your surgeon or clinic to provide you with the information."