Commuter chaos is expected for the first day back at work after Australia Day as Sydney train staff declare a 24-hour strike.

The Rail, Tram and Bus Union called the stoppage from 12.01am for both Sydney and NSW networks on January 29 as the latest salvo in an escalating pay dispute.

Train workers are demanding a six per cent yearly pay rise in each of the next four years, claiming to be the lowest paid in the nation.

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Mass delays are expected across Sydney's train and bus networks, as transport workers refuse to work overtime

Only RTBU members are allowed to strike with legal protection from repercussions with Sydney Trains, so some workers will keep working.

'We're disappointed it has come to this, but management and the NSW Government haven't left us with any other options,' RTBU NSW Secretary Alex Claassens said.

'Workers have been trying to negotiate a fair and reasonable enterprise agreement for well over six months now, but the NSW Government and Sydney and NSW Trains management have refused to bargain fairly.

'Not just around pay, but around basic conditions that impact their safety and the safety of commuters.

'The terrible way management and the NSW Government are willing to treat its hard-working employees has been laid bare for everyone to see lately.

'Workers are being stretched to capacity trying to deliver the shambolic new timetable, and now on top of this they're all being told they can't be guaranteed fair conditions and pay.'

The Monday strike is in addition to an indefinite ban on overtime beginning on January 25 that will cause delays and cancellations for day or weeks.

Sydney Trains relies on huge numbers of staff to do overtime to run its schedule, especially since the new timetable came into effect.

The strike was called as many of the union's members didn't think the overtime ban by itself went far enough.

With Sydney Trains relying on its drivers to do overtime to run its schedule, the move is expected to cause chaos for commuters

Mr Claassens said on Monday, about the overtime ban, that the government could stop the industrial action from going ahead if it met their demands.

'From Thursday the 25th of January, there will be an indefinite ban on overtime work. We've seen in the past few days that excessive overtime is leaving workers across the network fatigued and exhausted,' he said.

'The ban on overtime is important in order to protect our workmates and commuters.'

Mr Claasens said the union was 'incredibly disappointed we've had to get to this point'.

'No one wants to take industrial action, but we haven't been left with any other options at this stage,' he said.

'We're still hopeful that management and the government will come to the table and deliver an enterprise agreement that provides workers with the wages and conditions they deserve, so we don't have to take any more action. Our door is always open.'

Sydney Trains Chief Executive Howard Collins (pictured) as he speaks to the media

Mr Claasens said the NSW Government expected transport workers 'to do more with far less'.

He ensured commuters they would be kept updated with as much information as possible in lead up to next week's action.

'The last thing any railway worker wants to do is inconvenience commuters... but i'm sure everyone will understand, we've been forced to this point.'

Sydney Trains boss Howard Collins responded to the announcement on Tuesday saying it would create havoc for commuters.

'That will have an impact on the network... we are working on those contingency plans now,' he told reporters.

'It would be an important challenge for us and we would have to reschedule (trains).'