Research found that NHS Wales could have paid over £385,000 too much for just basic items over the course of a four-year contract.
One health board was found to have spent over £1,000 too much for bananas and another paid 94% more than the market price for cucumbers.
The Aneurin Bevan hospital board was found to potentially have spent over £43,000 too much for the five basic foods in one year. £13,000 of the total came from paying too much for bananas.
The research came to light through an investigation by the Sun newspaper and has resulted in the Welsh Audit Office being asked to step in.
Jonathan Isaby, chief executive of the Taxpayer’s Alliance, said: “"This is bananas. It's absolutely crucial that we don't pay over the odds for fruit and vegetables when money is so tight. Procurement in the NHS is an absolute mess, and the process needs to be fixed sooner rather than later. Every penny wasted is a penny that can't be spent on frontline care."
NHS Wales defended its actions by claiming its procurement practice considers far more than just the lowest price, citing food safety, ethical and responsible sourcing and high levels of customer service.