Labour is accusing Transport Minister Shane Ross of putting commuters in danger by failing to order new trains in time.
No new carriages will be in service before 2022.
The party's transport spokesman, Senator Kevin Humphreys says overcrowding is now a safety issue.
He says he saw a fellow passenger faint on a packed DART in recent days.
"Last week I was dealing with a young lady that fainted at Blackrock but actually only hit the floor of the DART at the Grand Canal Station. They were packed in like sardines and the pressure of the crowd kept this young lady upright."
Senator Humphreys says the new carriages will assist with the overcrowding but he says there has been delay after delay. He also says large Dublin offices should stagger their working hours to relieve pressure at rush hour.
