Westpac says "subscription traps" are still catching out online shoppers.

The bank said last year it had stopped more than $25 million in unwanted charges with a new payment block to stop the sales tactic.

It refers to the practice of overseas websites prompting shoppers to sign up to ongoing subscription payments without their knowledge.

Westpac said the amount had now risen to $40 million and more than $75,000 of payments was being blocked per day, on average.

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Head of customer care operations Peter Barnes said the businesses involved were not necessarily acting fraudulently because they often did disclose the details in their fine print.

"In our view, their money-making model is unethical," he said.

"Customers probably aren't reading the fine print like they should do when they sign up for things. The other factor to consider though is that the people who are conducting these subscription traps move around very quickly and they bounce from jurisdiction to jurisdiction or country to country. There's an amount of blocking that takes place but then there's a number of people that just pop up again."

He said most customers who spotted a problem with a subscription were people who checked their statements regularly and realised there were transactions that they had not expected.

People were often caught out by AI meal plans or training programmes, he said.

"Often people only realise they've signed up to a subscription until they see the further charges on their card, and when they contact the merchant to dispute it, it can be a difficult and time-consuming process.

"In the past two years we've seen more and more digital subscription services and e-commerce sites misleading shoppers by portraying themselves as being New Zealand-based. This makes them seem more trustworthy - when they don't actually have any presence here."

He said people should watch their transaction history closely and call the bank immediately if they had concerns.

Shoppers should be wary of offers that claimed to be discounts for people who acted quickly, he said. "They tend to trap some of our customers who get in before they actually think about what they're doing… they should think about what they're doing, because once they click that submit button, they're locked in. It does take a while to unwind some of this activity."