Marks and Spencer has said it is mystified by a claim by MEP Robert Kilroy-Silk that it uses "distorting" mirrors in its changing rooms.
Mr Kilroy-Silk sits as an independent MEP
Mr Kilroy-Silk has accused the store of misleading women with mirrors that make them look slimmer in its clothes.
He made the allegation in a written question in the European Parliament.
An M&S spokesman said: "Our mirrors are perfectly normal, standard mirrors. We are at a loss as to what he might be referring to."
In his question, Mr Kilroy-Silk asked if it was "conceivable that within the millions of EU regulations covering virtually every aspect of life in the EU" there was not one that made it illegal for M&S to have mirrors that "deliberately distort women's shapes".
Meglena Kuneva, EU Commissioner for consumer protection, replied that the alleged practice "may fall under the scope of the Unfair Commercial Practices Directive, adopted on 11 May 2005".
But she advised Mr Kilroy-Silk to take up the issue with the "national authorities" in the UK.
"Under the Directive, a commercial practice will be considered unfair if it is contrary to the requirements of professional diligence and if it materially distorts the economic behaviour of the average member of the group of consumers to whom the practice is addressed.
"However, it remains the exclusive competence of national authorities and courts to apply the national laws implementing EU law, and to investigate the practices of a particular company in the light of EU consumer legislation, in accordance with the principle of subsidiarity.
"The Commission would, therefore, suggest that the Honourable Member draws the attention of national authorities to this matter," Mrs Kuneva writes in her reply.
Mr Kilroy-Silk, who quit the UK Independence Party in 2004 following disagreements with its leadership, sits as an independent in Brussels and Strasbourg.
He was unavailable for comment.