It's a hot Friday and "dressdown" day - but some banks in London are concerned that scorching temperatures might prompt traders to bare it all - well, almost. "We don't want clients to come in and see a trading floor looking like a beach in the Bahamas," said a spokesperson for a large European bank.

Traders had been keenly looking forward to the now common "dress-down" day on Friday after temperatures reached a scorching 90 degrees in the City this week.

But with a long holiday weekend in London coming up, some worry that standards could be slipping.

A large US bank in London, for instance, issued a memo to staff on Thursday advising them to dress casually but smart yesterday - despite the hot weather.

"Tank tops, ripped jeans or shorts and sandals are not allowed," an analyst at the bank said. "So it's dress down, yes, but not quite."

If staff are meeting clients, dress-down day rules do not apply and it's back to the City uniform of suits and starched shirts. Visitors were warned yesterday that staff had dressed down.

Many other European countries have a far more relaxed dress code than the City, London's financial district, where a sports jacket and smart slacks will still raise eyebrows - unless it's Friday.

Dress-down days have become much more common, with many banks now allowing staff to dress casually on Fridays throughout the year. Others have dress-down days only during the summer. A couple of financial organisations in Dublin also operate dress-down days.

Some companies don't allow more relaxed outfits without at least a little bit of suffering - if staff want to dress down on a given day they have to pay money to a charity.