PARIS (AFP) - Fashion designer Karl Lagerfeld is suspected of having hidden more than €20 million (S$31 million) from French tax authorities using complex transactions between various companies, L'Express weekly reported Wednesday.

French authorities declined to comment citing the privacy of tax affairs.

A spokesman for Lagerfeld, who is artistic director for fashion house Chanel as well as having his own label, also declined to comment when contacted by AFP.

French tax authorities "suspect that in the space of six years the man with the ever-present black sunglasses omitted to declare €20 million" in France, wrote L'Express.

Lagerfeld, also an artist and photographer, is known for his trademark dark shades.

An investigation is focusing on the 7L bookshop in Paris, which Lagerfeld founded in 1999.

According to L'Express, the bookstore houses a photo studio owned by a British-based company, which takes in the revenue from Lagerfeld's photography work.

The bookstore loses money and thus does not pay taxes.

The news weekly said French tax authorities suspect the foreign transactions allowed the "concealing of the undeclared professional activity" of Lagerfeld as a photographer.

French authorities are also interested in the activities of two property investment companies and a tax adjustment Lagerfeld received in the 1990s.