Late last year, the supermarket quietly launched a service in which it pays customers for their unwanted gold trinkets.
Observers speculated that the move by the UK's biggest retailer into one of H&T's traditional areas was behind the share price fall. H&T declined to comment.
Tesco said on its website that it will pay customers £7.81 per gram of 9-carat gold. This compares to £7.59 at H Samuel and £6.50 at H&T. However last night Tesco said that from Thursday until the end of January, it will increase the payments to £10 per gram of 9-carat gold.
A spokesman for Tesco said: "Customers have been poorly served in this area, so we're pleased that we can trial a service that is transparent and offers market-leading value. Tesco Gold Exchange helps customers feel confident about raising a few extra pounds from their unwanted gold, enabling them to spend it on something more worthwhile.
"Plenty of people have old jewellery in the back of a drawer that is never worn and is of no great sentimental value but can be surprisingly valuable, particularly at a time when the price of gold is so strong."
