"The damp weather spells immediate devastation for gingerbread houses. The problem is the mild winter," spokesman at Sweden's leading gingerbread wholesaler Anna's, Aake Mattsson, told Swedish news agency TT.

Gingerbread houses are a popular Christmas tradition in Sweden and across the Nordic countries, with many people buying slabs of pre-baked gingerbread from stores which they decorate and stick together using icing sugar and brightly coloured confectionery.

While much of Sweden is usually gripped by freezing temperatures and heavy snow in December, southern parts of the country have recorded their mildest start to the month for decades.

In recent days Anna's has received some 40 complaints from angry customers whose carefully crafted gingerbread houses have collapsed.

As a seasoned gingerbread expert with 41 years in the business, Mattsson urged hopeful gingerbread architects to heat the ready-baked slabs in the oven briefly prior to assembly to remove any remaining moisture.

The risk of subsidence was also reduced if builders overcame the temptation to smother their cookie houses in excessive amounts of icing sugar.

"Too much (icing sugar) can result in dampness ... . It's a common problem," Mattsson told TT.

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