"They are a lemon, and it is the taxpayers who have paid for them", she said last night.
Ms Curran was a strident opponent of the decision to spend $150 million on 40 locomotives from China, saying New Zealand workers such as those at Dunedin's Hillside railway workshops should have got the job.
Labour leader David Shearer yesterday released an internal KiwiRail report outlining a long list of problems with the first 20 locomotives, which arrived in the country in 2009.
Some of the problems have been rectified by the manufacturer under warranty, but the report says some of those repairs failed and some sub-suppliers refused to supply parts under warranty.
KiwiRail chief executive Jim Quinn said last night "commissioning issues" with the locomotives were real but not insurmountable.
"We are frustrated ... But we have a structured process to rectify the issues and expect all the rectifications to be completed by September."
The company had expected the second batch of locomotives to arrive by the end of this year, but production was on hold until KiwiRail was sure design modifications had been made and "we don't run the risk of repeating these problems".
Delivery is expected next year.
The slow-down in the economy meant KiwiRail was happy to take a "more measured pace" to the delivery of the locomotives, Mr Quinn said.
The locomotives already in the country had travelled 1.9 million km so far and, once problems were rectified, they performed to expectations, he said.
Ms Curran said her information was some of the faults were serious.
"These are more than just teething problems. I understand the realignment of the alternators requires going into the heart of the engines and costs $250,000 per locomotive. That is $5 million across the fleet."
She had also been told the vibration and bearing issues were also serious and indicated a major underlying design fault.
Yesterday she lodged 10 Official Information Act requests with KiwiRail and Minister of Transport Steven Joyce seeking more information about the faults, the cost of rectifying them, and who was meeting that cost. She also planned to ask questions in the House later this week.
The leaked report came 10 days after Ms Curran discovered through an earlier Official Information Act request the brakes on all 500 Chinese-built freight wagons ordered by KiwiRail had to be replaced before they could hit the tracks last year.
New Zealand-built wagons would have been a better buy and would have ensured the retention of "Kiwi jobs and Kiwi skills", she said.
"This goes directly back to ministerial accountability ... Who instructed KiwiRail to buy the cheapest from China?"
Locomotive faults
• Control systems losing power and screen freezing; systems card and software upgrade needed.
• Bearing failures; bearings replaced but must be replaced again.
• Water pipes cracking and leaking.
• Turbo vent pipes require modification.
• Exciter base cracking causing excess vibration; six exciter bases failed again after first repair.
• Axle vibration resulting in excessive brush wear on alternator end-plate; problem improved but not yet eliminated.
• Engine-alternator realignment required.
• Compressor auxiliary units prone to shutting down; replaced with different type of unit.
• Silencers cracking and setting off fire alarm; silencers replaced.
• Basin pumps burning out; replaced.
