Consumers are calling on Tesco to backtrack on changes it has introduced to its Clubcard scheme, labelling them as unfair and saying that they will disadvantage thousands of loyal customers.

The UK’s biggest retailer’s popular Clubcard scheme offers shoppers the chance to collect points for money they spend in store and online. These points can then be changed into vouchers, redeemable on things such as restaurant meals at Pizza Express, Prezzo and Zizzi.

Up until now, some of those vouchers could be used for up to four times their face value, but Tesco earlier this week said that it was simplifying its system and that all vouchers would now be worth three times face value.

“We’ve listened to our customers and simplified our Clubcard Reward partners so that they’re more straightforward for everyone,” a Tesco spokesperson said.

“This means that from 15 January, we will offer customers three times the value of their vouchers,” the spokesperson added.

The change has provoked a wave of complaints from customers on social media. Many are particularly taking issue with the fact that Tesco had not provided any indication that the change would be introduced.

Martin Lewis, founder of consumer website MoneySavingExpert.com, on Tuesday described the move – “under the guise of simplification” – as “a slap in the face to thousands of loyal customers”.

He said that the issue is that the changes have been implemented “immediately without any notification”.

“Many people save their reward points month after month after month, waiting to redeem on a big item,” Mr Lewis said.

“These changes leave many of those people missing out on £50 or £100 – not good when so many are struggling.”

He called on Tesco to urgently review its policy, to “give a window of opportunity to those who’ve already saved substantial points, and will lose out by these changes, to still redeem at the prior value”.