A Ray Winstone-like voice is programmed to say "Don't even think about it" and "Put it down, put it back" as soon as the card is removed from the bag.
Rebecca Smith, Leanne Fischler and Kirsty Sneddon created the bag for a degree project.
The fourth-year students said the design was "very conceptual".
All three are in their final year at Duncan of Jordanstone College of Art and Design in Dundee.
The bag - designed to be a "unisex satchel" - has all the electronics hidden inside a false bottom.
A slot has been sewn in for a credit card which conceals an led light and a sensor which acts as a trigger to play the voice recordings.
Ms Fischler, 21, said: "As soon as you take the credit card out, it sends a signal and inside the bag we have a whole load of electronics which we coded ourselves using a platform called Arduino.
"It receives a signal when you take the credit card out and it tells the circuit board that the credit card's moved and it starts to play sequences from our recordings."
The students said at first the bag tried to deter you from spending money, saying things like "Don't you think that's a bit much?" and "Oh, not again". After a while the bag assumes you have made the purchase and starts to "publicly embarrass you".
However, if you put the credit card back right away it rewards you with a gruff: "I knew you could 'ear me".
Ms Smith, 21, told BBC Scotland they had been asked to make a project with an "element of whispering".
She said they had designed the bag as a concept, rather than hoping it would be manufactured for the mass-market.
"We're all passionate about using design to create change and starting conversations," she said.
"We want people to see it and interact with it."
Three students in Dundee have designed a handbag which berates you for spending money when you try to use your credit card.