The survey of 2,000 people suggests that cases of food poisoning are set to increase, a problem which reaches its peak in the summer months anyway.
Bob Martin, a food safety expert at the Food Standards Agency, told the BBC, "With most of us seeing our weekly shopping bills increase over the last few years, we are all looking for ways to get the most out of our shopping budget.
"Using leftover food is a good way of making our meals go further. However, unless we're careful, there's a chance we can risk food poisoning by not storing or handling them properly.
"It's tempting to just give your food a sniff to see if you think it's gone 'off', but food bugs like E.coli and Salmonella don't cause food to smell off, even when they may have grown to dangerous levels. So food could look and smell fine but still be harmful,” he added.
The official advice from the FSA is that use by dates must be followed, and that leftovers should usually go straight in the fridge and be eaten within two days after that.