So many posters are splashed in store windows the world over that it’s rare for anyone to really pay that much attention to them, let alone snap and tweet them.

But that’s just what TV freelance writer Chris Dodd did.

The poster refers to a ‘Fifty pence challenge’ designed for Sainsbury’s staff to encourage every customer to spend an extra 50p every time they shop between now and the end of the year.

So Chris helpfully pointed out the poster to the Sainsbury’s social media team, and someone called Ross quickly got back to him asking which store the posters were in.

But Chris Dodd was keen to share his supermarket find…

Ross was then forced to admit that this poster was indeed meant for ‘staff areas’ and not for the public to see.

Since the first image was posted on Twitter yesterday evening, the social network has been awash with angry and amused consumers using the #50pchallenge hashtag.

One user tweeted: ‘First we have to scan & bag our own groceries, now we're responsible for increasing basket spend?!’

A Sainsbury’s spokesperson said: “We often use posters to make store targets fun and achievable for our colleagues.

“They are intended for colleague areas in the store, but this one was mistakenly put on public display.”