The grocers have upped the ante on coupons with a swathe of new deals at category level.

Supermarkets have in recent months increasingly used money-off vouchers to win customers in the ferociously competitive sector but have so far focused on money off an overall spend.

Tesco is running a £10 money-off voucher offer on a £40 spend on online clothing as well as £5 off a £30 spend on entertainment products.

Sainsbury’s is offering a £30 voucher to shoppers who spend £200 on furniture online and £50 off a £350 spend on electricals on the web.

Research by coupon provider Valassis showed that in 2011 an extra 66 million voucher redemptions were made by shoppers compared with 2010, bringing the total to almost 230 million. Morrisons last week ran a £5 off a £40 spend offer within days of Tesco chief executive Philip Clarke describing the prevalence of vouchers in the market as “unhelpful”.

Sainsbury’s chief executive Justin King last week argued Sainsbury’s Brand Match vouchers are the most attractive. He maintained: “Not all vouchers are equal.”

Meanwhile Aldi today waded in to the voucher battle with a £5 off a £35 spend voucher deal in the Daily Mail. The discounter advertised the offer on the paper’s front page. The coupons aer valid until June 29.