Twenty per cent of V/Line trains did not run to Albury-Wodonga in March, in one of the worst reliability performances since records began.
While COVID-19 impacts including the border closure were linked to poor reliability in February (32 per cent) and July (43.9 per cent) of last year, there were no restrictions on the service last month.
Euroa MP Steph Ryan said the Victorian government had to replace the rolling stock as promised.
"During March, six of the 25 N-class trains that service regional Victoria including the North East and Seymour line were non-operational," she said.
"It is abundantly clear that the N-class locos are way past their design life - they should have been replaced years ago.
"Some of the trains are now between 34 to 36 years old."
IN OTHER NEWS:
Ms Ryan said the government must ensure the six new V/Locity trains are on tracks and ready to go as promised by mid-year following the completion of track upgrades.
"Jacinta Allan and Jaclyn Symes are both on the record stating that the new trains would be on operational as soon as the track was complete," she said.
"I think I can speak for all North East commuters and say that we are much looking forward to the arrival of the six new VLocity trains which the government has promised will start taking passengers in the second half of 2021."
It was announced in October a $10 million facility would be built at Albury Railway Station to house upgraded trains.
The line has achieved 100 per cent reliability only twice.