On 9th May 2012 the Government announced their intention to create a new drug driving offence, which will make it much easier for the police to take action against drug drivers.
Under these new proposals it will be an offence to drive a motor vehicle if you have specified controlled drugs in excess of specified limits in your body.
The Department for Transport estimates that approximately 140 of all road deaths in 2010 were related to drug impaired driving.  An independent review of drink and drug driving law in 2010 recommended that a new offence should be developed.  
How will the law change?
The new offence is set out in the Crime and Courts Bill.   If the Bill becomes law it will be illegal to drive or be in charge of a motor vehicle with specified controlled drugs in your bloodstream over the limit set for each drug.
The exact drugs and limits covered by the offence will be set following advice from an expert panel and a public consultation.
Devices for police officers to use at the roadside to screen for drugs in the body are expected to receive approval by the end of the year.  The penalty for the new offence will be maximum of 6 months imprisonment and / or up to £5,000 fine, and an automatic driving ban of at least 12 months.  
What is the current law?
It is already an offence to drive whilst impaired by drugs. This covers both illegal and legal/prescription drugs. If your driving has been negatively affected by the drugs you have taken, you can get a heavy fine, be disqualified from driving or even go to prison.  This will remain in place alongside the new drug drive offence.
Updated: 10th May 2012