Police in the West Midlands have been told not to wear brightly-coloured pants or visible thongs in a lesson in fashion which has caused anger amongst officers.

Guidelines published by the force advised officers and staff to make sure undergarments were appropriate. A message to staff read: “Underwear should be of an appropriate colour to be inconspicuous underneath your uniform.”

It provoked a furious outburst from several officers who questioned why their bosses are getting their knickers in a twist.

One sergeant said: “We are not a scouting organisation made up of young children who need nannying.

“As we are all adults, personal pride should drive folks to maintain that professional appearance by shaving before going on duty, having clean boots and tidy uniform.”

A constable added: “It is ridiculous. They are basically telling us what underwear to wear to work.

“A couple of sergeants have jokingly been saying there would be spot checks. It is outrageous.”

The guidelines were part of a wider force “revised uniform, equipment and appearance policy” that followed the introduction of some new items of uniform.

Officers were warned baseball caps should only be worn by officers in certain units, including dog teams and marksmen.

New-style black operational shirts must be worn fully zipped up, or with the zip “no more than 40mm” from the top.

Officers were also told to wear hats and helmets as soon as they get out of vehicles, while those on patrol must always wear stab vests.

All forces have uniform policies, but most appear to have stopped short of issuing diktats on underwear.

West Midlands Assistant Chief Constable Sharon Rowe said managers must “challenge” inappropriate dress.

She added: “The adoption of standard, corporate, professional uniform and equipment is crucial to how we are viewed by members of the public.”

West Midlands Police said there was no new policy on underwear, but all officers and staff who come into contact with the public should adopt a “common sense approach when choosing what underwear is worn when on duty, so they remain smart”.