The 8.5 per cent improvement to £52.4m in the three months to last Saturday represented a sixth consecutive quarter of growth and came after the chain launched new products and targeted customer service standards.

Own-store sales were 5.1 per cent higher at £33.8m, with like-for-like sales 0.5 per cent stronger. This was down on the 1.2 per cent growth seen in the previous quarter, although Thorntons said it was a pleasing performance given the timing of Easter shortened its key trading period.

Thorntons chief executive Mike Davies said the business had maintained a "steady course", adding that he was confident the chain would deliver on City expectations for the financial year.

He added: "Our strategy has succeeded in delivering product innovation and improvements to our stores and to customer service."

However, Mr Davies warned the chain was also seeing cost hikes "marginally ahead" of the company's expectations.

Derbyshire-based Thorntons has 379 stores, with another 252 operating on a franchise basis.

Recent initiatives have included the re-launch of its continental range and a children's selection with no artificial colours or added preservatives. It has also reported improvements in staff turnover and morale following the roll-out of its 'You are the Difference' programme.

Commercial sales, such as through supermarkets, rose 14.5 per cent in the quarter, while Thorntons Direct reported a gain of 27.7 per cent to £2.2m.

Despite the sales progress, Thorntons shares fell 7 per cent as investors reacted to the guidance about rising costs.