Shares in Tesco have fallen 6% in the last week after the UK retailer unveiled disappointing sales results for the six-week Christmas period. Investors reacted negatively to figures showing a 1.2% decline in sales at Tesco’s international business, with sales in European stores particularly weak (-2%).

The supermarket giant blamed an intensely competitive market in Poland for the decline in sales in Europe, while the death of the King of Thailand also negatively affected sales in the Thail market.

In Ireland, Tesco reported a 0.7% decline in sales during the busy Christmas period. However, this reflects the decline in the value of sterling in 2016. Sales volumes in Ireland have increased year on year.

The only bright spot for Tesco was a 0.7% growth in sales at its UK stores, which was above market expectations. Overall, the Tesco group posted marginal sales growth of 0.3% this Christmas period.

Despite the weak sales performance in its international stores, Tesco chief executive Dave Lewis remained upbeat on the results.

“We are very encouraged by the sustained strong progress that we are making across the group. In the UK, we saw our eighth consecutive quarter of volume growth and delivered a third successful Christmas,” said Lewis.