An interim report has found a backlog of almost 40,000 defects plaguing Sydney's "fragile" train network, and things are on track to get worse.

NSW Transport Minister Jo Haylen said the "train network isn't working", and was being stretched to its limits.

The review has been lead by National Transport Commission Chair Carolyn Walsh, and was requested by Ms Haylen after Labor won government in March.

The first part of a review into the transport system, handed down today, found industrial action had created massive delays in fixing faults, with the reliability and resilience of the system at an all-time low.

One of Ms Haylen's first acts in government was to request a review into Sydney Trains, after being "alarmed" by initial briefings about the state's rail infrastructure.

"Our train network is neither reliable nor resilient and we need to act now to fix it," Ms Haylen said.

The review was also sparked by three major incidents in March, most notably a communications outage which brought the entire network to a halt, leaving thousands stranded.

National Transport Commission Chair Carolyn Walsh and the panel had come up with 12 recommendations to improve the network's reliability.

The NSW Government has accepted all of them.

"If we don't act now there will be more incidents, and more severe incidents," Ms Haylen said.

The panel said the most crucial recommendation is a "maintenance blitz" to bring the backlog down to "acceptable levels" within 12 months.

It also recommended communications be improved both among staff and with customers who were impacted by track issues.

Sydney Trains will also now be responsible for timetabling, instead of Transport for NSW.

"The challenge ahead of us over the next 12 months is not about changing the timetable, it's about making better use of the time we've got available to access the network," Sydney Trains CEO Matthew Longland said.

Today's interim report pinned a lot of issues on a timetable introduced in 2017, which was designed to address skyrocketing passenger demand at the time.

But the panel found it was "far too tight" and made it difficult to maintain services without major disruptions.

"The reliability and resilience of Sydney Trains' operations has been fragile since the introduction of the 2017 timetable," the interim report found.

It also found the number of trains arriving on time had dropped.

Cancellations and delays on the rise

Last month, there were nearly 40,000 infrastructure-related defects reported, such as track and electrical issues.

Of those, more than 1,200 are considered  "priority 1" which have to be checked every week, such as a crack in the rail line.

That number has significantly risen since industrial action began over enterprise bargaining in 2021.

"Issues causing delays are at their highest levels in the past decade," the interim report found.

Shadow Transport Minister Natalie Ward blamed Labor for the industrial action which made the network's problems worse.

"They were created out of industrial action and delay. They were created out of them playing their union mates over time, and they need to now hold them to account," Ms Ward said.

"Commuters should be at the centre of this, not unions."

In the next phase of the review, the panel will investigate ways to improve efficiency in the network, the performance of the fleet and safety.

A final report will be handed down in October.