New research has backed up the growing suspicion that merchants are profiteering from credit card surcharges, with some businesses stinging customers, on average, three times the fee they actually pay card companies.

What's more, some merchants are starting to apply surcharges to debit cards and even to cash transactions.

The latest survey of merchants by banking researcher East & Partners has found that the average surcharge is now 2.55 per cent, a figure that it says is in "stark contrast" to the average merchant fee for Bankcard, MasterCard and Visa of 0.81 per cent.

It's also higher than the average merchant fee charged by American Express, at 1.92 per cent, and Diners Club, at 2.12 per cent.

If surcharges were strictly about cost recovery, as intended, they would be on average 0.81 per cent or a little higher for Amex or Diners Club users. Yet it's not uncommon for merchants to pin the blame on card companies when customers query such charges.

The incidence of businesses applying surcharges is growing and there have been significant increases in surcharges in some areas, the principal analyst at East, Paul Dowling, says. In the non-retail sector - which includes electricity, gas and telephone companies - the survey found the incidence of surcharging had more than doubled in the past year, so that one in three non-retail businesses now applies a surcharge to transactions.

Surcharges by such businesses also jumped from an average of 2.3 per cent on top of a transaction to a whopping 5 per cent. The average retail surcharge was steady at 2.3 per cent.

Card users pay dearly