Shares in womenswear retailer Bonmarché have plummeted 24% after the firm issued a profit warning, saying “unseasonably hot weather” in September melted sales of its autumn ranges.

The retailer said it expects like-for-like sales at its shops to plunge by 8% in the second quarter and first half of the year. As a result, Bonmarche said full year pre-tax profit will come in at between £5m and £7m. Shares fell to 87p.

The firm said: “Trading in September has been extremely poor, largely as a consequence of the unseasonably hot weather which has not favoured sales of our new autumn ranges.

“We approach the beginning of the second half of the year facing considerable uncertainty as to market conditions. The hot September has prevented us from gaining a representative measure of the strength of the autumn ranges, and our perception is that the clothing market generally has become more challenging.”

In June, the value chain said full-year pre-tax profits dropped by more than a fifth to £9.6m, down from £12.4m in 2015, as it grappled with an “unusually difficult year”.

New boss Helen Connolly, who took up the role earlier this year, said she is “formulating my plans for the future”, adding: “The direction of travel is right, but the effectiveness of execution needs to improve. My plans are therefore likely to focus on improving the clarity of the customer proposition and operational improvements in all channels rather than a major strategic repositioning.”

Kate Calvert, analyst at Investec, said the shares will “remain friendless” until Ms Connolly outlines her strategy and performance improves.