Pre-tax profit melted to£5.2 million in the year to June 24, from£8.1 million the previous year. Like-for-like sales fell 3.7 per cent for the full year, but improved in the second half when like-for-like sales slid 1.8 per cent.
Thorntons chairman John von Spreckelsen said: 'While the decline in sales and profits is disappointing, the prospects and potential of the business remain positive. Following a prolonged period of corporate uncertainty for the group, our focus will be on creating sustainable growth in sales and profit.
'The board has been informed by Peter Burdon of his intention to step down as chief executive.'
The hot weather in July last year prompted a decline in the sale of chocolates, but the retailer said this was partly offset by high ice cream sales. In August and early September, sales were in line with expectations, but performance over Christmas was poor.
Thorntons will focus on enhancing its retail offer and claimed it was well placed to benefit from trends towards healthier eating as shoppers place 'quality and health at the forefront of their confectionery choices'.
Good progress had been made with online arm Thorntons Direct, the retailer said, where sales increased 6.4 per cent to£5.5 million.
Burdon will remain as chief executive until a successor has been appointed.