There has been a 56% increase in the amount of cannabis seized by Revenue this year.
According to details released by Revenue under the Freedom of Information Act, €5m worth of cannabis herb and resin was seized in the first five months of 2019.
The figure is up from €3.2m in the same period last year.
Senator Aodhan Ó Ríordáin, a former junior justice minister, says it shows how big a problem Ireland has with cannabis.
"It is a welcome development," said Mr Ó Ríordáin.
"It shows that Revenue are working hard but it also shows that the cannabis issue we have in the country is quite big.
"We are still waiting for the publication of a report from a working group on possession of drugs for personal use.
"And within that, we need to do more than just seize cannabis off people, but try and direct people who have addiction issues to service led, health led, services.
There has also been a 260% increase in the amount of illegal tobacco seized which equates to €1.8m worth of raids in 2019.
The level of illicit mineral oil recovered by Revenue is also up by 20% this year with more than 72,000 litres seized.
Revenue has also seized €153,000 worth of cash this year.