Earlier this month Visa removed Heartland, along with RBS WorldPay, from its list of PCI DSS compliant service providers following major data breaches that put the card details of millions of people at risk.

The move prompted confusion among merchants concerned they may judged to be non compliant for using the two payments processors and therefore open to fines.

However, Gartner analyst Avivah Litan says she has received a statement from Visa confirming merchants can continue doing business with the two firms without threat of penalty charges.

This stance will remain valid as long as Heartland and RBS continue to work towards revalidating their PCI compliance, which they are expected to complete within weeks.

"Visa clearly did not want to risk putting the processors out of business, partly because of the potentially enormous disruption to their hundreds of thousands of merchant customers," says Litan.

Heartland has seized on the Gartner statement in an attempt to reassure customers and fight off competitors.

In a letter on the firm's Web site, chairman and CEO Robert Carr says merchants may have been approached by competitors "making false claims" about fines.

"Through a series of cease and desist letters, Heartland has informed competitors that their untrue and misleading claims are baseless and unlawful. Heartland intends to initiate legal action against them if they do not immediately stop making these claims," says Carr.

He also says that if a card brand attempts to penalise a customer for using Heartland, the firm will defend the merchant and reimburse it if the fine is found to be legally enforceable.