The UK's big four supermarkets will disclose how they fared over the Christmas period this week. The Kantar Worldpanel will also disclose the market share figures of Tesco, Sainsbury's, Morrisons and Asda over the key trading period.

All four are expected to report a slide in their performance during the vital festive period, indicating the changing shopping habits and the growth of discounters Aldi and Lidl, according to the Guardian.

While Sainsbury's is expected to report a 0.7% decline in sales at established stores in the three months to the end of December, Morrisons is expected to reveal a 2% dip in the nine weeks to 3 January. Tesco – which saw a drop in sales between 2% and 3% in the three months to the end of November – is also expected to report a fall in Christmas numbers.

Asda, which is owned by Walmart, is the other member of the so-called "big four" and is supposed to have witnessed a 3.5% drop in sales during the Christmas period, according to estimates by analysts. The supermarket giant had recently cranked up the pressure on its rivals by committing another £500m (€665.7m, $726.4m) towards slashing prices.

Shareholders of Sainsbury's will particularly be interested in the trading updates as they have to make a call on whether or not to support the supermarket's plan to bid for Home Retail Group, the owner of Argos. Sainsbury's is planning for a higher takeover bid for Home Retail after its recent £1bn cash and a share bid were rejected.

However, some analysts seem to disapprove of the move as they have warned that a bid for Argos could distract Sainsbury's, which has been doing better than its closest rivals in recent years. While the big four have lost in Christmas sales, discounters Aldi and Lidl gained, with both chains seeing a double-digit sales growth.