Power company Jemena has confirmed that 23 smart meters were deliberately tampered with since December last year.

The alarm was raised earlier this month after a number of smart metres in the northern suburbs were sprayed with a chemical substance, believed to be chloride, to make them fail.

Police have taken over the investigation.

The affected meters in Pascoe Vale, Coburg, Hadfield, Footscray and Preston failed but did not cause fires.

Jemena spokesman Scott Parker says it is only a matter of time before someone is injured.

"Tampering with any electrical equipment is very wreckless and extremely dangerous," he said.

"We call on the perpetrator to stop before somebody gets seriously hurt."

He admits smart meters are vulnerable because they are located outside of the home.

"Unfortunately the meters are accessible to somebody who wants to deliberately damage them," he said.

"The tests confirm it is not the smart meters themselves which are failing."