The vouchers were being offered via Facebook page called 'Asda Stores', in a post which encouraged users to like, share and comment "thanks" to be in with a chance of winning.
Many shoppers may have been lured into entering the giveaway to help fund the expensive Christmas shop.
The first post on the page was made on 30 November, followed by multiple others which accumulated thousands of comments and shares.
However, the supermarket chain told the M.E.N that the page and voucher giveaway is not affiliated to Asda.
A spokesperson also confirmed that Facebook have been contacted about the fake profile, with a request to take the page down.
The only official accounts for the supermarket those titled 'Asda' on both Facebook and Twitter.
More Christmas scams to look out for
The Asda voucher giveaway is just one of many scams to be aware of this festive season, with numerous fraudulent schemes cropping up around Christmas.
Some of the most common scams include:
Facebook holiday or gift competition
Typically offering a holiday or this year's must have gift as the prize, Facebook users will be asked to like or share the page to be in with a chance of winning.
They may also be directed to a website by clicking a link, where they will be asked to enter their personal information.
Email or text competition
'Competition winners' are tricked into claiming their fake prize by sending a prize release payment or delivery fee, only for their money to be stolen by scammers.
Gift card giveaway
These scams are common on social media or messaging apps, such as WhatsApp, and ask recipients for their personal details in order to claim their gift card.
These scams often come from unreputable businesses and ask for your personal details so you can be entered into a raffle or prize draw.