If SMRT personnel did, indeed, falsify maintenance records, then tough action should be taken against them, observers said.

The lapse resulted in flooding that led to a 20-hour breakdown of the North-South Line last month.

The rail operator revealed yesterday that though records had been submitted for quarterly maintenance work on the Bishan pump system on three separate occasions since December last year, the works had not been carried out as required.

Mr Yee Chia Hsing, a member of the Government Parliamentary Committee (GPC) for Transport, said he was "disappointed and shocked" by the irresponsible attitudes of the workers who had not conducted the required maintenance work.

As many people depend on public transport for their daily commute, the MP for Chua Chu Kang GRC said further measures must be taken to check that maintenance work has been carried out so that such incidents do not recur.

Mountbatten MP Lim Biow Chuan, who also sits on the GPC for Transport, said that while SMRT staff were generally "diligent, conscientious and honest", serious action must be taken against all those found responsible.

"This will signal that those who fail their responsibilities face serious consequences," he said.

National University of Singapore transport researcher Lee Der Horng said the admission pointed to organisational issues within SMRT, something the rail operator itself has admitted to.

In a press conference two weeks ago, SMRT chief executive Desmond Kuek said that there were "deep-seated cultural issues" within the firm that led to the Oct 7 disruption.

Dr Lee said: "Even if they have the most up-to-date technology and a perfectly deployed system, it comes down to the people who are responsible."

Hiring external experts for inspections - as SMRT plans to do - may not be easy as most such experts already work for the rail operators, he added.

The fact that the neglect of maintenance work was not detected for an entire year suggests that the problem is deep-seated, said Singapore University of Social Sciences senior lecturer Park Byung Joon. Such underlying organisational issues must be addressed, he said.

One commuter, Ms Hanum Harlini, hoped that the additional checks to be introduced by SMRT would help address maintenance issues on the rail network.

The 39-year-old pre-school therapist added that while irresponsible workers should face action, diligent staff should also be rewarded for doing their part in maintaining the MRT system.

Even if routine maintenance is conducted, it is no longer a guarantee that Singapore's increasingly complex rail system will work smoothly, said Singapore Institute of Technology assistant professor Zhou Yi, a chartered railway engineer.

Instead, rail operators here must beef up their capabilities in predictive and preventive maintenance, he said.