Nationwide has revealed that it could take up to six years to fully integrate Virgin Money, following its acquisition of the rival bank.

The building society defended the £2. billion takeover during its annual general meeting (AGM) on Wednesday. Nationwide's chief executive, Debbie Crosbie, stated that there had been a "huge amount of careful consideration of both the risks and opportunities" involved in the purchase of Virgin Money.

She said that she was "very confident that the profits will more than cover any costs of integrating the business". One of the reasons for the acquisition was the bank's range of credit cards, according to Crosbie. However, she acknowledged that the integration process is likely to take several years.

This means that Virgin Money customers will continue to see the bank as a separate brand, with its own high street branches, for between four and six years. This is partly due to the "challenges" of improving Virgin Money's customer service and IT systems.

Crosbie assured members that the building society would be "on the case", following concerns raised about Virgin Money's support systems. She also reassured that new and existing customers of Virgin Money can be "comfortable in the knowledge that it is owned by a mutual, not listed shareholders".

Eventually, Virgin Money savers and borrowers are set to become Nationwide customers, but this will not happen automatically. Crucially, Nationwide still needs to get the approval of regulators in the UK before it can go ahead with buying the bank founded by business mogul Sir Richard Branson.

It is expecting to get a decision from the Competition and Markets Authority and the Prudential Regulation Authority in September, paving the way for the takeover to complete in the autumn should it get the green light.