Campaigners have lost the right to bring a £14bn ($18bn) mega class action suit against MasterCard alleging the US credit card firm had overcharged 46 million people over almost two decades.

The Competition Appeals Tribunal in London threw out the claim agreeing with MasterCard that the grievance was unsuitable to be brought as a collective action suit. This blocks the case from going to court.

The claim against MasterCard is that it allegedly infringed EU competition law by imposing high card charges that were passed on to shoppers over a 16-year period ending in 2008.

MasterCard argued the grievance did not meet the set criteria for a collective action to proceed saying the claim contained a massive class of individuals with disparate claims.

If it had gone to court the case would have been one of the largest and most complex in UK legal history. It would have tested the limits of the Britain' 2015 Consumer Rights Act, which introduced US-style class actions for breaches of British or EU competition law.

The lawsuit alleged that cross-border charges on the use of MasterCard debit and credit cards — known as interchange fees — were a significant cost for retailers. But this cost was then passed on to consumers in the form of higher prices for goods and services, it claimed.

The case was brought forward by US law firm Quinn Emanuel Urquhart & Sullivan after MasterCard lost a 2007 appeal of a European Commission ruling that its fees were anti-competitive.

The firm was retained by Walter Merricks, the UK's former financial ombudsman, who spearhead the class action claim.

Campaigners disappointed

Merricks said he was considering an appeal and told the Financial Times he was "surprised and disappointed" by the decision.

He added: "The new collective action regime was introduced by the Consumer Rights Act to overcome the difficulty for consumers seeking to recover losses from competition law infringements. I am concerned that this new regime designed to benefit consumers may never get off the ground."

The number of potential claimants involved in the proposed action was so large because the law allows individuals to be automatically included in this type of litigation unless they opt out.

Campaigners for the class action argued the suit ought to include anyone who bought goods or services from UK businesses that accepted MasterCards between May 1992 and June 2008, provided they were UK residents and aged 16 or over.