A Bradford-based building society that wrongly overcharged mortgage holders millions of pounds in repayments apologised today for the "decidedly embarrassing" error.

Monthly payments were accidentally withdrawn twice from 25,000 homeowners' accounts due to "human error", a spokesman for the Yorkshire Building Society admitted.

Affected customers were left with cash shortfalls of hundreds of pounds over the weekend as the mistake happened late last Friday and could not properly be rectified until Monday.

The society, based on Rooley Lane, made efforts to put matters right as soon as possible by refunding the money as well as paying extra charges people may have incurred as a result of the withdrawals.

It was estimated that this would cost the firm around £10,000.

Banks, building societies and cash machine controllers were also alerted to the error to make sure customers would have enough money to tide them over for Saturday and Sunday.

Extra staff worked in the Member Contact Centre over the weekend to deal with customers' calls, including on Sunday, when it is usually closed.

On Saturday 30 extra staff were drafted in and opening hours were extended from 9am until 1pm to 5pm.

Spokesman David Holmes said 20 extra employees worked from 9am until 2pm on Sunday, at which point calls stopped coming through.

Mr Holmes said: "It is decidedly embarrassing. We pride ourselves on our service levels. When something like this happens it is not good so the onus is on us to make it right."

He said the Financial Services Authority had been informed but had decided to take a "relaxed" attitude towards the matter as it had been rapidly dealt with by the society.

The company had been feeding through orders to the BACS national clearing system instructing payments to be taken from the 130,000 accounts when the error occurred.

There had appeared to be a problem sending through the last batch of 25,000 so they were split into two batches of 12,500 and sent again, only for managers to realise later that this had resulted in mortgage holders being double charged.

Mr Holmes said: "When it was discovered that BACS had deducted two amounts from customers' accounts it was impossible for them to backtrack on Friday afternoon."

He added: "We have had 35 people contact us saying it cost them money and they have been fully reimbursed, no questions asked."