The centre-left government announced on Monday that it had raised the amount of marijuana a person can carry without being arrested for dealing.
Health Minister Livia Turco said she had issued a decree with the help of the Justice Ministry increasing the amount of marijuana that is legal for personal use from 500 milligrams to 1 gram in terms of pure, active ingredient.
The new quantity is the equivalent of 30-40 joints.
Turco stressed that drug users caught with up to a gram of marijuana could still face a fine but would not be arrested or sent to jail as potential dealers.
"We cannot risk thousands of youths being imprisoned or subject to criminal proceedings for having smoked a joint. Unfortunately, that is what has been happening up until now," Turco said.
She stressed that the government would now push ahead with a a more radical revision of the country's drug legislation, passed by the previous, centre-right government earlier this year.
The February law enshrined a "zero tolerance" approach to all types of drugs.
It made possession of hard and soft ones a potentially criminal offence with jail terms ranging from six to 20 years for suppliers.
Critics of the law were particularly angry at the thresholds set for personal drug possession, which they said were too low.
Apart from the 500mg for marijuana, they were: 750mg for cocaine (or some 5 doses), 250mg for heroin (or some 10 shots), 750mg for ecstasy (or five tablets), 500mg for amphetamines and 150mg for LSD.
People caught with more than these quantities automatically face criminal proceedings for dealing unless they can prove that personal use only is intended.
Members of the centre-right opposition condemned Monday's marijuana revision, accusing the government of encouraging drug users.
"This is the thin end of the wedge. The government wants to legalise all drugs," said the rightist National Alliance (AN).
When the February law was passed, supporters including AN said it marked the end of tolerance towards marijuana users and affirmed the principle that all drugs are bad.
They denied critics' claims that 'recreational' drug users would be penalised.
But centre-left MPs attacked the regulated amounts, saying they were far too low and could result in thousands of soft drug users being sent to prison.
They noted that very few European countries define specific quantities as thresholds for criminal proceedings and argued that even in the states that do, the amounts are consistently higher.
According to recent statistics, 33% of Italian teenagers between the ages of 15 and 19 have smoked pot at least once, while 10-12% have tried cocaine, 11% ecstasy and 7-10% crack.
Among adult Italians, almost 10% are reported to use pot on a regular basis.
There are an estimated 300,000-320,000 heroin addicts in Italy, more than 20,000 of whom are in jail. In 2001, 150,300 Italians were treated for drug addiction.
