The chairman of the Royal Bank of Scotland (RBS) said that its IT systems needed to improve at the lender's annual meeting.
The admission comes after the taxpayer-backed bank's latest embarrassing IT glitch that saw 600,000 payments fail to go through to customers last week.
The problems affected all four of its banking brands - NatWest, RBS, Ulster Bank and private bank Coutts.
At the Edinburgh meeting, Sir Philip Hampton told shareholders: "As last week's processing delays showed, whilst we have invested heavily in rationalising and simplifying our systems and processes, we need to continue to improve overall performance."
It is another blow to the group, which has been hit by a number of IT failures in recent years.
In 2013, RBS's online service was disrupted by a denial-of-service attack.
And last November, the state-backed group was hit with a £56 million fine from the Bank of England and City watchdog the Financial Conduct Authority (FCA) after a computer failure in 2012 saw as many as 6.5 million customers at NatWest and Ulster Bank unable to make payments for as long as three weeks.
Sir Philip said his six years at the head of the bank had been full of ups and downs, but he was sure he was leaving the lender in a stronger position.
He said: "There have been highs and lows along the way, but overall RBS has made great progress since 2009. It has been fundamentally rebuilt - it is now a bank that is much safer in capital strength, in structure and increasingly on behaviour."
The annual meeting also comes as the Government prepares to begin selling the taxpayer's 79% stake in the bank after Chancellor George Osborne announced the plans in his annual Mansion House speech.
He said the stake sale would begin in the coming months, but admitted the Government stands to make a loss of about £7 billion if the entire stake is sold off in one go.
Investors cheered the plans to return RBS to private hands, with shares rising the day after the announcement - although Labour queried Mr Osborne's "rush to sell".
Sir Philip will step down as chairman and will be replaced by Sir Howard Davies, who is currently chairing the Airports Commission, in September.