The big four supermarkets have enjoyed a steep rise in non-food sales over the past three years - at the expense of the high street specialists.

More than 62% of shoppers use grocery stores for general shopping compared with 45% three years ago boosting their collective non-food spend to a whopping £19.7bn, according to a survey by Verdict Research. This would rise to £24.4bn in 2012, it predicted.

More shoppers now bought clothes regularly from Asda or Tesco than they did from Bhs, Gap or H&M, according to the survey. The big four also boasted bigger market shares than health and beauty specialist Superdrug.

"The supermarkets are no longer just grocers," said consulting director Nick Saunders. "We expect them to build on this over the next few years and that will make life hard for specialists."