The cancellations on Monday come after the rail operator cancelled 92 services on Saturday due to "unexpected train crew changes", including 44 on the T1 Northern, North Shore and Western Line.

Underscoring the challenges for front-line workers in dealing with "a massive increase" in patronage, the reports reveal the number of station staff has fallen by a quarter since Sydney Trains' first year of operation in 2013 when it replaced Railcorp.

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Severe disruptions across the city's rail network last week revealed how Sydney Trains had been caught short by a lack of drivers to cope with an increase in services as a result of a new timetable. That timetable has reduced the ability of the system to recover from delays caused by major incidents.

While Sydney Trains said last week it was "flat out" hiring extra staff, its annual reports reveal the size of its workforce rose only slightly in its first four years as an entity despite the demands of a booming population.

The total number of train crew such as drivers and guards was 2469 at the end of last June, an increase of just 22 people since its first year of existence as an entity in the 2013-14 financial year.

According to Sydney Trains, however, those figures under-sell the size of the increase in train crew. Excluding line managers, supervisors and trainers, the number of train crew increased by 4.4 per cent from mid-2014 to the end of 2017, from 2357 to 2461.

The annual reports also show station staff have been cut significantly in the past four years, falling from 1918 people in the 2013-14 financial year to 1408 in 2016-17.

The introduction of the Opal card has enabled Sydney Trains to remove ticket-selling positions.

Labor leader Luke Foley said it was staggering to see how few train crew had been hired since 2013.

"Proper workforce planning wasn't done to ensure the new timetable had the resources in place before it was rolled out, and that's part of the reason we saw a shambolic meltdown of the train network last week," he said.

The government said last week that 225 new staff had been hired for Sydney Trains, while another 165 staff would be in training by the end of January. It takes a year to train drivers before they can be allowed to operate a passenger service.

A spokesman for Sydney Trains said it had cancelled a "small number of trains on Monday due to staff availability".

"To minimise disruptions we have analysed load data and cancelled services that are typically the least busy, are outside of peak hours or have another train scheduled soon after it," he said.

Sydney Trains said staff availability did affect the "timetable recovery" early last week, along with extreme weather conditions and signal failures.

"We do not expect staffing levels to be an ongoing issue. Since 2016 we have employed 226 trainee drivers, with over 70 of them already working on the network," the spokesman said. "We have also increased frontline station staff."

The cancellations of services on Monday would not be permanent, he said.

Sydney's rail network is in for another major challenge on Monday when an upgrade to a junction at Hornsby – described as the busiest and most complex in Australia – is completed and opened to large volumes of trains.

Any incidents on the realigned tracks at Hornsby have the potential to cause significant disruptions to the entire rail network.

After railway workers voted in favour of protected industrial action,unions will meet on Monday to discuss their next steps in their standoff with Sydney Trains over a new four-year pay deal.

Senior union leaders will also attend a "workshop" on Tuesday with top rail officials, including planners, to look at ways to refine the new timetable to ensure the network can recover from delays to train services caused by major incidents.

Sydney Trains' total workforce at the end of June was 9978, a rise of 1.5 per cent since the 2013-14 financial year.

smh.com.au