There’s growing speculation the introduction of Melbourne’s new high capacity trains will be delayed, with multiple sources telling 9News the $2.3 billion project is “not going well”.

The first of the trains is due to start taking passengers by mid-year, but has so far been confined to the depot.

The first of the trains is due to start taking passengers by mid-year, but has so far been confined to the depot. (Nine)

Before entering passenger service, the train is required to complete 10,000 kilometres of testing on the Pakenham line.

The testing regime is logistically challenging; the first 2,500 kilometres can only be conducted at night once regular train services have stopped running, while the next 5,000 kilometres can only occur outside of peak hours.

Those tests had been due to start earlier this year, but the train is still undergoing static testing, where teams check the functioning of mechanical and electrical systems brakes and traction while the train is stationary.

The Andrews government awarded a contract to build 65 of the new seven carriage trains to the Chinese-backed Evolution Rail consortium in 2016. (Nine)

Opposition Transport Spokesman David Davis said tests had identified a number of issues.

“It seems that there are problems with these carriages, it seems that there are genuine issues about the quality of the build, and issues around the weight”, he said.

Despite that, a spokesperson for the Department of Transport said the testing program was progressing well.

Opposition Transport Spokesman David Davis said tests had identified a number of issues. (Nine)

The Andrews government awarded a contract to build 65 of the new seven carriage trains to the Chinese-backed Evolution Rail consortium in 2016.

The trains are designed to carry 20% more passengers than the existing fleet on the busy Dandenong and Sunbury corridors, and will eventually run through the Metro tunnel.

Evolution Rail deferred questions about the project to the Department of Transport.