According to new Canadian research, bottled water holds more bacteria than tap water.

The study conducted by a team of 70 scientists from the C-crest Laboratories in Montreal found that bottled water is not as pure as first thought.

"Heterotrophic bacteria counts in some of the bottles were found to be in revolting figures of 100 times more than the permitted limit," Microbiologist Dr Sonish Azam, who worked on the study, said.

"Bottled water is not expected to be free from microorganisms but the [level] observed in this study is surprisingly very high."

She said that there is no need to drink bottled water if good quality tap water is available.

"Unsurprisingly, the consumer assumes that since bottled water carries a price tag, it is purer and safer than most tap water," she said.

Despite the study finding large amounts of bacteria in bottled water, Dr Azam said this bacteria was not likely to cause disease.

"But the high levels of bacteria in bottled water could pose a risk for vulnerable populations such as pregnant women, infants, immunocompromised patients and the elderly," she said.

The Dieticians Association of Australia's Queensland spokesperson Julie Gilbert said if good quality tap water is available, it is the best option.

"If on the rare occasion tap water is unsafe, bottled water is a good alternative," she said.

The DDA does not believe bottling water is good practice when we have a safe water supply in Australia.

"Bottled water is a healthy option when tap water is not available, convenient or safe," she said.

"And bottled water is a better choice than other packaged drinks. When eating away from home, DAA recommends taking a reusable water bottle from home, or asking for tap water."