Halifax says it has mended the systems glitch which permitted investors to deal in other people's shares.
Halifax Building Society sent out a written statement today saying that its internet share dealing service resumed at 8am, after being out of action over the weekend due to a serious security breach.
Registered customers were able to access other people's accounts and trade their shares when the Stock Exchange opened last Friday morning. The service was suspended at 10.30 am.
The statement said that the fault, a glitch caused by a minor modification to the system's programme, has been eliminated.
It said that after a comprehensive audit it was found that "all trades carried out on Friday were legitimate and that customers accounts are in order," but a spokesperson confirmed that no warning was on the Web site about the fault.
Critics complained that Britain's biggest mortgage lender continued to take registrations without notifying people of the problem and it posted no reassurances or explanation via the Website.
Halifax said that ShareXpress online customers are being contacted today to confirm that their accounts are in order.
David Walkden, general manager of Halifax Direct, told the Financial Times that he did not expect to see an erosion of consumer confidence in e-commerce as a result of the incident. He said: "Confidence comes from how you respond in making it right for the customer if there has been a problem."
Using photocatalysts to convert carbon dioxide into usable energy such as methane or ethane