Britain is to review data on breast cancer risks resulting from implants.
While stressing there was still no evidence to justify fears of a cancer link, Health Minister Andrew Lansley said he had asked an expert group to review British and foreign data about the implants, which are used by about 42,000 British women.
"I am concerned and I'm unhappy about the consistency and quality of data that has been provided by (implant) providers to the regulator," Lansley said.
"I've asked Professor Sir Bruce Keogh, the medical director of the NHS, now to lead an expert group which will report to me early next week on the data."
The group's review will include "what the data is saying in this country and overseas, and... the regulation of quality and safety in the private cosmetic surgery sector", he said.
Earlier this month French authorities advised 30,000 women to have PIP implants removed because of an increased risk of rupture, despite insisting there is no proven link to cancer.
Britain has not recommended this step and has sought to reassure women that there is no evidence of a cancer risk, but Lansley said new data had come to light this week that had caused him some concern.
"We have been pursuing the question of what the data says. We have seen conflicting evidence," he told reporters.
There are media reports that the investigation was triggered by a leading cosmetic surgery firm, which privately warned ministers that the proportion of women at risk is as high as 8 per cent, rather than the 1 per cent previously claimed in the UK.
The company is responsible for about 4,000 of the UK's PIP implants, but if an 8 per cent rupture rate proves accurate and is widely replicated, it could mean a total of 3,200 women are affected. In France, where authorities shut down PIP last year, the risk of rupture is said to be about 5 per cent, and women have been advised to have the implants removed - a move backed by British surgeons but not, so far, by ministers.
But if the risk rate is confirmed as being substantially higher in the UK than in France, pressure will grow for the Department of Health to follow the French Health Minister, Xavier Bertrand, in urging women to have them removed. Abnormal rupture rates of the implants, which contain industrial-strength silicone commonly used in mattresses, emerged in 2009. Symptoms can include lumps around the implant or in the under-arm, inflammation in the breast tissue and a hardening of the breast.
Dr Susanne Ludgate, clinical director of the Medicines and Healthcare products Regulatory Agency (MHRA), also said concerns had been raised by "conflicting data" coming from the cosmetic surgery industry. "It raises doubts about the surveillance and reporting of incidents by these companies. We will urgently work to identify where problems may be," she added.