SMRT managed to get 95 per cent of its bus services running today despite about 60 China-born bus drivers not turning up for work.

The operator used its own standby drivers, it was revealed at a Ministry of Manpower press conference that has concluded

On Monday, when 102 drivers refused to work because of unhappiness over salary, SMRT got 90 per cent of its services running.

Acting Minister Tan Chuan-Jin had harsh words for the drivers at the conference, reiterating that their action was "unacceptable".

The illegal strike is being investigated by the police.

Mr Tan said that under the Criminal Law (Temporary Provisions) Act, a strike of essential service workers is illegal if 14 days' notice was not given.

Under the Act, those found guilty can be fined not more than $2,000 and/or a prison term of not more than a year.