Staples is among some leading companies targeted by New York state to end to what it calls fraudulent selling practices involving web-based loyalty discount shopping programmes.

The attorney general office of New York state has issued subpoenas to 22 e-commerce retailers about their dealings with three leading providers of “post-transaction” sales services - Webloyalty, Vertrue and Affinion/Trilegiant.

The attorney general’s office said it was investigating practices “that deceptively link unsuspecting consumers to fee-based membership programs that charge unauthorised fees under the guise of discount offers.”