Superdry, best known for its coats and hoodies, has warned of weaker than expected profits, saying customers have not bought extra winter layers this year.
It now expects annual profits of between £55m and £70m - analysts had been expecting around £84m.
Superdry blamed warm weather, consumer uncertainty and a lack of innovation.
The company is considering closing stores as part of a cost cutting drive to save £50m by 2022.
“Superdry had a difficult first half, impacted by unseasonably warm weather across our major markets, a consumer economy that is increasingly discount driven and the issues we are addressing in product mix and range,” said Euan Sutherland, Superdry’s chief executive officer.
Underlying profit before tax almost halved in the first half of the year, to £12.9m.
The retailer is a third of the way through an 18-month strategy to re-energise the brand which includes introducing childrenswear and 100% organic cotton products.
Mr Sutherland said the firm’s “over-reliance” on jackets and sweatshirts was partly to blame for flagging sales.
He will oversee an efficiency drive which will include reviewing the number and size of their stores, and exploring renegotiating rents between now and March 2019.
Superdry’s shares fell by 20% on Wednesday morning.