The Zurich-based bank is trying to improve its image and regain the faith of clients after it was bailed out during the recent financial crisis, posting the biggest loss in Swiss corporate history.

The 52-page internal document advises staff in five pilot scheme branches on how to make a good impression with customers, bizarrely including underwear advice.

Men’s underwear ‘should be of good quality and easily washable, but still remain undetectable,’ whatever that means.

Women are advised to wear flesh-coloured underwear and stockings, and are warned against too-tight underwear and shoes.

Women are also told that wearing make-up gives the impression of competence, and all staff are advised to avoid smelly foods and tobacco.

A spokesman from the bank said: ‘They are meant as recommendations and not as hard and fast rules.’

‘It remains to be decided whether the guidelines will be extended to all 300 Swiss branches, depending on how they are received by staff in the five pilot branches.’