From today, tough new drink-driving laws come into effect in Western Australia, with some offenders forced to install alcohol interlock devices in their cars.

The scheme applies to people who record high blood-alcohol levels, and repeat offenders who will have to install the devices which require them to take a breath test before they can start the engine.

They will be fitted for a minimum of six months from the driver's disqualification period.

Earlier this year, the Road Safety Minister Liza Harvey said the move would go a long way to tackling drink-driving.

Offenders to foot the bill

Criminal lawyer Andrew Tehan said many people would not be aware they would have to pay to install and service the devices.

"Works out to be about $1,600 dollars for the minimum six month period and that can obviously be extended if the person can't evidence that they've separated drinking alcohol and driving with clean results," Mr Tehan said.

The regulations bring Western Australia in line with most other states and territories, although Victoria has the strictest regime.

There the devices are mandatory for anyone convicted of drink-driving.

In WA, an offender would have to have a blood-alcohol reading higher than 0.15, be a repeat offender, or refuse a breath test.

Mr Tehan said similar measures in other jurisdictions appeared to have an impact.

"My understanding is that it has been effective in other states, the laws are harsh, they're harsh for a reason, the harsh penalties obviously reflect our society's tough stance on drink-driving."

Fines will be imposed on anyone who tampers with the interlock device data, get someone else to do the breath test, or drive a vehicle without a device.

Mr Tehan said in other some other jurisdictions the maximum penalty for tampering is a prison term, although that "would only occur in very rare cases".