An MTR engineer-turned-lawmaker said on Thursday that a full-day closure of the Kwun Tong line for maintenance is essential, adding that more short-term closures are likely to be required as the network ages.

Gary Zhang, who worked for the corporation before entering politics, made the comments on RTHK's Hong Kong Today programme a day after the MTR announced that no trains would operate on the stretch between Prince Edward and Ho Man Tin on July 28.

"I understand that the replacement work this time has to be carried out at very high levels within the tunnel. And it's very close to the train power supply system" he told RTHK's Samantha Butler:

"So therefore, it's basically technically impossible to just rely on one night of non-traffic hours to complete the job."

Zhang added that the MTR was confident of completing the work within the allotted time.

He said it was very likely that more such closures would be required as the network's oldest routes, the Kwun Tong and Tsuen Wan lines, reach the end of their design lifespan. Zhang noted that the routes opened in the 1980s and had a design life of approximately 50 years.

He said structural work like that being carried out on July 28 was "very critical to the railway operations safety and the reliability".

Announcing the work yesterday, the MTR said July 28 was chosen because it fell on a Sunday during the summer holiday, when usage was likely to be light.

It noted that the other lines running through the four affected stations would remain open, adding that a free bus services would run between Yau Ma Tei, Ho Man Tin and Whampoa.