Hong Kong's rail operator should have contingency plans and measures to deal with crowds at turnstiles as well as network issues that delay QR-code payments, lawmaker Gary Zhang said on Monday.

Over the weekend, the MTR said relatively more people used their phones to pay with QR codes at the same time at Lok Ma Chau on Friday, and that the mobile data network and station Wi-Fi facilities could not handle the surge in demand.

It pointed out that at one point, commuters were allowed to leave paid areas without having to tap out.

Speaking on an RTHK programme, Zhang said connection problems were not only limited to the station, but also affected Lok Ma Chau Bridge.

"No mobile signals were received even on the bridge, so people had to change to the station's Wi-Fi. When everyone used the station's internet, it exceeded the daily capacity of the router, leading to a system freeze," he said.

To prevent such incidents from occurring, Zhang said that relevant staff should be put on standby.

"The stability of the telecommunications network is linked to the stations' server and engine rooms. I think the MTR should follow up with internet service providers and see if they can arrange maintenance staff to stand by at the scene during festivals or holidays, so any problems can be resolved quickly," he said.

Zhang added that the MTR should beef up manpower at stations as well, as more people are opting to use QR codes to travel.