The trial involving the four alleged ringleaders of last November's illegal bus strike will start on March 4, after they refused to plead guilty to amended charges of participating in the strike.

The prosecution will call more than 30 witnesses, including SMRT officials, SMRT drivers and the police, to the stand. Defence lawyer Andrew Goh, who is representing driver Liu Xiangying, 33, said he intends to call 10 witnesses including drivers and doctors.

The four men, Gao Yue Qiang, 32, Wang Xianjie, 39, He Jun Ling, 32, and Liu, were accused of instigating an illegal strike on Nov 26 which involved 171 drivers from China and another 88 who stayed away from work the next day.

They were unhappy with their salaries and living conditions. The trial will go on for five days from Mar 4 before resuming at a later date.