German MPs have voted to back a new legal driving limit of 3.5 nanograms of tetrahydrocannabinol (THC) — the main psychoactive component of cannabis — per millilitre of blood.

Although criticised by right-leaning opposition MPs who wanted the limit set to zero, experts told the government that 3.5 nanograms of THC was comparable to a blood alcohol content of 0.02 per cent, The Times reports.

Stefanie Iwersen-Bergman, head of toxicology at the University Medical Centre Hamburg-Eppendorf, said: “Studies show that the THC level in occasional users drops to less than one nanogram per millilitre of serum within around eight hours [of consuming a joint].”

However, regular cannabis users have been warned that they could remain above the legal limit for longer.

Germany recently became the first major European country to legalise cannabis for personal recreational use.