SMRT has been slapped with a maximum fine of S$2 million for the twin breakdowns last December.
Transport regulator, the Land Transport Authority, said the fines -- S$1 million each for the Dec 15 and Dec 17 incidents on the North-South Line -- is the maximum penalty under the Rapid Transit Systems Act.
The LTA said in a press release that SMRT had failed to "exercise due diligence and vigilance expected of a public transport operator, and to maintain its network in good and efficient working condition".
Further internal investigation found that both incidents were preventable.
The authority said it will continue to work closely with SMRT to implement last week's ommittee of Inquiry's recommendations.
It will also work with the rail operators to put in place a "more holistic and robust framework" for maintenance issues, so problems can be detected and fixed early.
The SMRT acknowledged the fine and said the recent release of the Committee of Inquiry report had provided it with "valuable insights into enhancements needed in our previous maintenance regime which was regularly validated by LTA."
SMRT said it would implement further improvements, and work closely with the LTA to enhance reliability and service levels for the benefit of our commuters."
The $2 million fine will be donated to the Public Transport Fund to help needy families with transport fares.
Last week, Transport Minister Lui Tuck Yew also said the government and LTA accepted share of the blame in failing to ensure SMRT's responsibilities were kept in check.
Addressing the recent Committee of Inquiry (COI) findings in Parliament last week, Minister Lui said they shared part of the blame in the twin MRT disruptions in December last year that affected more than 200,000 commuters.