Signalling issues at Melbourne's Southern Cross Station have caused widespread delays for peak hour commuters.

Metro Trains said there were major delays to all City Loop services from about 6:00pm.

There were delays on all major lines, except Stony Point.

All outbound trains were diverted to Flinders Street Station.

One commuter described the scenes as hectic.

A Metro Trains spokeswoman said fitters had been on site and fixed the issue just after 9:00pm.

Opposition spokesman David Hodgett earlier said huge queues of commuters had been forming at some of the platforms

"The City Loop train network is in chaos tonight, it's in absolute meltdown, people have experienced long delays, major delays," he said.

"Feedback I'm getting is it's actually quite dangerous, some of the crowding on some of the platforms and people are quite angry with the lack of information."

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