The number of passengers enduring “crush capacity” on Sydney's inner west light rail line or being left behind on platforms will worsen unless the Berejiklian government buys more trams to boost the frequency of services, “sensitive” documents warn.

And even if new trams are bought, it will be up to three years before they are running on the line because of the length of time it takes to procure and commission them.

The "sensitive" documents warn of "most, if not all, services" reaching "crush capacity" by 2021 without trams running every six minutes during peak periods. Credit:Louise Kennerley

The confidential government reports, obtained by the Herald using freedom of information laws, warn the existing fleet of 12 trams will “likely not meet forecast patronage growth” over the next two years, and commuters will “require alternative transport options” along parts of the rail corridor.

“Patronage growth shows that by 2021 most, if not all, services will be at crush capacity under the current eight-minute headway arrangement,” one of the documents states.