The government has rejected calls for a more extensive examination of platforms at Hung Hom MTR Station that are at the heart of a construction scandal which has cast doubts about safety.
During Legco's railways subcommittee meeting on Friday, the pan-democrats' convenor Claudia Mo and pro-government lawmaker Michael Tien said the 84 spot checks the MTR has agreed to do isn't enough.
Critics had pointed out that the current number of checks planned translates into less than one percent of couplers installed. Some experts say only five percent or more would make the investigation meaningful.
Transport Secretary Frank Chan said the number of spot checks ordered is sufficient, and checking five percent would not be practical.
He compared the sample size to those used for a census. "We have in Hong Kong 7 million people. If we use 5 percent, then we have to poll 350,000 Hong Kong people. This is not practical," the secretary said.
Chan also said the sampling will be carried out independently by Hong Kong University experts and if any problems are found, more sampling will be done.