The Co-operative Bank's ethics chief was today forced to defend a new television advert depicting a man having "Ethics & Values" etched on his back after it emerged the tattoo was a fake.

Aired for the first time tonight, the ad aims to highlight what sets the bank apart from other lenders as it prepares to publish its latest ethical policy later this autumn following a poll of 74,000 customers and staff.

Laura Carstensen, chair of its values and ethics committee, told BBC Radio 4's Today programme: "These days people see a tattoo as a way to very publicly or sometimes very privately make a statement about an enduring commitment to something.

"That's the feeling we are tapping into. It's an enduring statement and so is our commitment to values and ethics."

She said that these represented "the golden thread that will run through absolutely everything we do".

Pressed on the fact that it was not a real tattoo, she said: "It's an ad. I think we have a pretty media savvy public out there who will understand what we are trying to say with this and I think it's a pretty powerful ad."

The bank has had an ethical policy since 1992 and says that this has seen it turn away more than £1 billion of business.

Its new campaign aims to help reverse the decline in current account holders which saw 38,000 customers leaving in the first half of this year following what it described as a "hurricane of negative publicity".

The bank nearly collapsed in 2013 after a £1.5 billion hole was discovered in its balance sheet and had to be rescued by bondholders including US hedge funds who now own nearly 80% of the business.

Ms Carstensen was asked about these investors, and whether it would be ethical if any of them were to be channelling their profits offshore.

She told Today: "We have a range of shareholders and the ethical policy and our commitment to uphold cooperative values, that's about the bank and how the bank does business and how the bank is in the world."

Chief executive Niall Booker said: "We understand that the difficulties the bank has faced in the last year are bound to test customers' beliefs, but now the bank is stronger we want to reassure them that we have not forgotten the values and ethics that set us apart and remain a key part of our success in the future."