Consumers are spending more on chocolate with sales of luxury boxes booming and those of healthier dark chocolate nearly doubling, according to a study published on Friday.

A survey by consumer research company Mintel showed the value of chocolate sales between 2005 and 2007 rose by 10 percent, up sharply from growth of only 1 percent between 2003 and 2005.

Luxury chocolate sales were up 46 percent over the two-year period, reaching 140 million pounds.

"Consumers are cutting back on their 'unhealthy' treats. Yet, when they do indulge, they often want the best in terms of quality and luxury," Mintel said.

"Brits may not be eating chocolate as often as the used to, but they are certainly splashing out more on premium varieties," Mintel senior market analyst Mathilde Dudouit said.

Mintel was unable to provide volume sales figures.

Mintel said a further 5 percent growth was expected this year, bringing the value of the British chocolate market to 2.23 billion pounds by the end of 2008.

"These trends will continue to help stem the chocolate market meltdown, with sales of all chocolate set for a further 17 percent growth in the five years to 2013," Mintel said.

Mintel said sales of dark chocolate almost doubled between 2005 and 2007, reaching 85 million pounds last year.