Scientists claim tea drinkers who choose cheaper supermarket blends could have a higher risk of developing bone and teeth problems.
A study by the University of Derby found that cheaper tea blends contain enough fluoride to put people drinking at least four cups a day - the average daily intake - over their daily recommended limit, increasing the risk of such illnesses.
Researchers said the following supermarket blends were found to have an average of 6 mg of fluoride per litre:
- Asda Smartprice
- Tesco Value
- Morrisons Value
- Sainsbury's Basics
These economy blends contained between 75% to 120% of the recommended daily intake of fluoride, the scientists claim.
The following branded black blends were found to have an average of 3.3 mg per litre:
- PG Tips
Pure blends Oolong and Pu'er teas had the lowest concentrations of fluoride - an average of 0.7 mg per litre - the study states.
One litre is the equivalent of four cups of tea.
Laura Chan, who carried out the study with Professor Aradhana Mehra and Professor Paul Lynch, said excess fluoride can have a detrimental effect on health.
"Dental fluorosis, the mottling of tooth enamel, and skeletal fluorosis, pain and damage to bones and joints through calcification, can occur" Ms Chan said.
The study is published in journal Food Research International.