Both Sainsbury's and market leader Tesco TSCO.L have warned of a drop in profit this year as soaring inflation raises their costs, hurting their margins, while at the same time hitting shoppers' spending power. Britain's supermarkets are generally not passing on to consumers all of the cost price inflation they are seeing which is lowering their profits. Sainsbury's said its latest investment in the prices of daily essential items and festive products would take its two-year total to more than 550 million pounds.