Denmark’s financial regulator has called in the police to investigate a bank involved in jewellery chain Pandora’s float.

Nordea, a Swedish bank, is accused of publishing bullish research urging clients to buy shares in the jeweller, which is chaired by former Asda boss Allan Leighton, without disclosing its 3.9% stake in the retailer, according to The Times.

The jewellery chain, famed for its charm bracelets, floated in October with a valuation of more than £3bn. Pandora sent out a profit warning this month and dismissed its chief executive Mikkel Olesen.

Since its flotation Pandora’s stock has collapsed 80% as growth stalled as a result of it hiking its prices.

Denmark’s financial authority said Nordea should have told investors that it had an interest in the jeweller, rather than rely on a general disclaimer. Nordea admitted to The Times that it had made a mistake and said it would be changing its procedures.

Pandora’s EBIDTA plunged 6.2% in its second quarter, and UK sales plummeted 13.1%. The brand sells through 420 stores in the UK, including its own stand-alone shops.

The jeweller warned that revenue growth for the year, previously expected to be 30%, would be nil. The profit warning wiped around two thirds off Pandora’s market value.