Shoppers are being warned to ignore fake supermarket vouchers offering £50 off coupons.

The posts say stores are celebrating their 'anniversary' and that everyone who shares the link will receive a £50 voucher.

A number of versions of the vouchers have been shared widely on Facebook over the past few days but stores have confirmed they are a fake.

A warning from Morrisons added: "We are aware of a number of spam emails, text messages and social media posts from third-parties posing as Morrisons for the purpose of fraudulent activity.

"If you receive one of these suspicious messages, please do not click any links, open attachments or enter personal information.

"We would never ask for your personal details in order to redeem a voucher.

"If you believe you have been contacted please contact us on '0345 611 6111' or call Action Fraud on '0300 123 2040'.

"You can also visit '' to report fraudulent activity to the authorities."

Essex Trading Standards has also issued a warning after a similar Tesco voucher was being shared across the country.

A spokesman added: "Nobody who participates will receive a coupon.

"If you see one of these giveaway posts, don’t be tempted to participate.

"You have no chance of winning the promised prize, and you may risk your privacy and security by sharing your personal information with online scammers."

How does the scam work?

The scam is a form of phishing, where fraudsters pose as reputable organisations to gain personal details.

Upon completing the survey, the victim is urged to share the link in order to get their voucher and say 'Thanks'.

This helps legitimise the scam, says Action Fraud, as Facebook friends will think it has come from a trusted source.

How do I know if a voucher is real or fake?

You can ask the store if they have any promotions currently running or check their website.

Keep an eye on official Facebook and Twitter feeds for genuine offers from the supermarkets and other retailers.