Westpac has dropped its American Express companion card from its credit card portfolio – the last of the big banks to do so.

Mozo.com.au reports in its latest Banking Roundup that the parties terminated their partnership last month.

Amex companion cards entered the market about a decade ago as a way of giving consumers a way to maximise their reward points.

Banks issued a Visa or Mastercard credit card as well as an Amex card under one credit card account. The Amex card had a high points earn rate and the Visa or MasterCard guaranteed universal acceptance.

Companion card arrangements were a response to the tightening of interchange pricing under four-party card issuing arrangements.

Companion card arrangements lost their appeal when, in 2016, interchange-like payments to issuers in the Amex companion card system were made subject to equivalent regulation as applied to MasterCard and Visa credit card systems.

One of the big impacts of interchange reform has been the dilution of reward programs and in recent years this has impacted Amex along with Visa and Mastercard issuers.