Authorities have seized more than €160 million worth of cannabis in Ireland in the past four years – with almost half of it discovered last year alone.

New figures released by the Department of Justice show that more than €70 million worth of cannabis was seized in 2012, with the majority coming from a huge increase in the number of cannabis plants seized from sophisticated grow-houses throughout the country.

More than 55,00 cannabis plants were seized last year, up from 26,500 in 2011 and a mere 3,900 in 2009. The amount of cannabis herb seized last year was the lowest in three years, but still accounted for €19 million.

The information was provided through analyses by the Forensic Science Laboratory and all of the valuations are based on estimated street values. The figures were provided by Minister for Justice Alan Shatter in response to a question by Patrick Nulty TD.

Cannabis is the most commonly used illegal drug in Ireland with 25 per cent of people saying they have taken it at least once in their lifetime. Six per cent of people have used it in the last year and 3 per cent have used it in the last month, according to the most recent national survey of drug prevalence.

The figures:
2012:
• Cannabis herb: 994,039 grams seized Value: 19.8 million
• Cannabis resin: 1,263,654 grams seized Value: €7.5 million
• Cannabis plants: 55,485 plants seized Value: €44.3 million
Total: €71.8 million

2011:
• Cannabis herb: 1,825,669 grams Value: €21.9 million
• Cannabis resin: 1,632,246 grams Value: €9.7 million
• Cannabis plants: 26,531 plants. Value: €10.6 million
Total: €42.3 million

2010:
• Cannabis herb: 1,087,301 grams Value: €13 million
• Cannabis resin: 1,304,162 grams Value: €7.8 million
• Cannabis plants: 14,227 plants Value: €5.6 million
Total: €26.5 million

2009:
• Cannabis herb: 612,613 grams Value: €7.3 million
• Cannabis resign: 2,053,921 grams Value: €12. 3 million
• Cannabis plants: 3,919 plants Value: €1.5 million
Total: €21.2 million