Abba’s trade-mark wacky style was influenced by Swedish tax laws, a recently released book has revealed.

The group’s bold style was affected by Swedish laws that allowed the cost of costumes to be deducted from tax – but only as long as they were so outrageous they couldn’t possibly be worn on the streets.

The bright colours, sparkles and spangles were regularly seen on the foursome in their marathon of chart domination during the 1970s and have since been the influence for many a fancy dress costume.

This news was released in their new book, Abba: The Official Photo Book, which was published to mark 40 years since Waterloo won them the Eurovision Song Contest.

Reflecting on the group’s heyday, Björn Ulvaeus said:

“In my honest opinion we looked like nuts in those years. Nobody can have been as badly dressed on stage as we were.”

In 2007 Ulvaeus was wrongly accused of failing to pay 85m kronor (.£7.9m) in Swedish taxes between 1999 and 2005, and went on to successfully appeal against the decision, according to a report by the Guardian.