Half of Melbourne's morning peak train services are almost double their capacity and transport authorities are covering up the real statistics, according to the Greens.

Key points: Services affected by delayed, cancelled trains not included in stats, Greens say

Services affected by delayed, cancelled trains not included in stats, Greens say Lines significantly exceeding 800-passenger capacity benchmark

Lines significantly exceeding 800-passenger capacity benchmark Victorian Government "working to improve" network's capacity

Data obtained under Freedom of Information showed the capacity on six of the city's 11 rail lines exceeded the 800 passenger benchmark during the morning rush, the party said.

Greens Victorian leader Greg Barber said infrastructure had not kept up with the population boom in parts of the outer suburbs and the city's growth corridors, and accused Public Transport Victoria of "fudging" its statistics.

"The standard is 800 people per train, that's considered to be overloaded, but on most lines pretty close to half the trains are now exceeding that standard," Mr Barber said.

"I think they've broken a new record in this survey because they had 1,262 people on one train [on the Pakenham line]."

He said the survey, which is conducted twice a year, compared figures from May 2015 to the same month in 2014.

"We got the raw data from the survey, and it turns out they've been fudging the figures," Mr Barber said

"Anytime a train gets cancelled or delayed, that causes overcrowding, but they actually exclude that from their figures because they say that's not normal.

"But cancellations and delays are normal, they're happening all the time."

Victorian Government 'getting on' with improving network

Mr Barber said there had been a lack of investment by multiple governments over the past decade to improve the infrastructure needed to run trains more frequently.

"If they don't hurry up and fix the signalling system, make the improvements to allow them to run extra trains, then things will just get worse," he said.

"And they're already pretty bad."

Victorian Public Transport Minister Jacinta Allan said the Government was taking action to improve rail services after the former Coalition government "wasted" its four years in office.

"It's about making sure that the train system has enough trains, enough capacity to move the people who want to use it," Ms Allan said.

"We know more and more people are choosing to use public transport, and with Melbourne's growing population, we know those two factors are adding to it being a service that people are using more and more.

"We want people to use public transport, and that's exactly why the Andrews Government hasn't wasted a moment in getting on with those important public transport projects like ordering bigger trains, improving signalling, getting on with the Metro rail tunnel, removing level crossings, so we can provide that extra capacity."