LONDON (Reuters) – Britain’s payments regulator on Tuesday fined five payments companies including Mastercard a total of 33 million pounds ($45.01 million) for cartel behaviour involving prepaid cards issued to vulnerable people on welfare benefits.

Mastercard received the largest fine of 31.56 million pounds ($43.04 million). The other companies fined were allpay, Advanced Payment Solution, Prepaid Financial Services and Sulion.

The Payment Systems Regulator (PSR) said the firms broke competition law by agreeing not to compete or poach each other’s customers on pre-paid cards offered by local authorities to distribute welfare payments to vulnerable people.

The cartel meant recipients of the cards – who included the homeless, victims of domestic abuse and asylum seekers – could have missed out on cheaper or better-quality products, the regulator said.

The PSR previously announced in March last year it planned to fine the five companies in preliminary findings. It said on Tuesday it had concluded the investigation.

The regulator said during the course of the investigation, all the parties settled and admitted breaking the law.

“This investigation and the significant fines we have imposed send a clear message that the PSR has zero tolerance for cartel behaviour,” said Chris Hemsley, Managing Director of the Payment Systems Regulator.

($1 = 0.7332 pounds)

(This story corrects regulator name in paragraph 3)

(Reporting by Iain Withers; Editing by Rachel Armstrong)