Tesco Bank has neared the completion of a highly-troubled data migration project.

The bank, which is fully run by the supermarket giant but was until 2008 a joint venture with the Royal Bank of Scotland, locked out online customers for three days in June as it experienced serious problems moving RBS data onto its own systems.

As Tesco reported a 7.2 percent rise in group sales for the third quarter, including banking revenues, it detailed the latest stage of the migration .

"The transition of the remaining products [mortgages and current accounts] to our own systems infrastructure is now complete, with the exception of credit cards, which are on track for migration in early 2012," it said in a statement.

However, it said, loan balances "reduced temporarily" as it "focused on completing the migration of these accounts" to its own systems.

The migration has run more smoothly since chief executive – and former IT director – Philip Clarke slowed down the project two months ago.

At the time, he said, the company had "taken the decision to slow down the introduction of new products until we have settled in the new bank team, processes and systems".

During the height of the problems in June, scores of angry Tesco Bank customers wrote on Computerworld UK about the problems they were having with accessing their money, and with reaching a customer service assistant to obtain advice. Many said they would move their money to another bank.