"Aucklanders are taking to public transport like never before," Mr Brown said.
"We need assurances from KiwiRail that they are doing everything they can to ensure there is no repeat of this disruption.
"As Aucklanders look forward to electrification and the arrival of our new train fleet, they need confidence that train services are reliable and on time."
Auckland rail operator Veolia Transport said a cable was cut overnight, affecting all train services between Pukekohe and Puhinui this morning.
"As a result limited services are running on this section of track and major delays are likely to be experienced as the peak travel period approaches," Veolia said in a statement.
"This affects all Southern Line passengers and delays and full capacity carriages are expected on the Manukau/Eastern Lines. These services will be running as they can and not on the published timetable. Western and Onehunga Line services are not affected and are running to timetable."
Commuters were advised to seek alternative transport.
Veolia said some taxi shuttles were operating between Pukekohe and Papakura but customers travelling between these two stations were advised to seek alternative transport where possible, while rail replacement buses were being arranged from Papakura towards the city.
Last night's fault in Auckland happened about 6.30pm at the end of peak-hour traffic, causing people to pour out of the station searching for buses and taxis. An announcement at Britomart said services had been stopped due to a signal failure in Wellington.
However, Kiwirail said it was an Auckland-based problem and not a repeat of the debacle in April which crippled Auckland's rail network.
Kiwirail spokeswoman Kimberley Brady said the technical fault happened on the Auckland rail network system and an investigation had begun into what caused it.
She said Kiwirail was happy the system was restored within half-an-hour, "but we'll obviously investigate the cause to try and make sure it doesn't happen again".
A spokeswoman for Veolia said train control asked them to halt all services while the problem was fixed.
"Passengers that were waiting at stations were advised they could use their AT Hopcards and rail tickets on normal bus services. Obviously, due to the time of day we couldn't organise rail replacement buses."
The outage affected the southern and eastern lines, while western line trains were operating, although with delays.
KiwiRail chief executive Jim Quinn said his organisation had launched investigations into both incidents.
"We understand how much frustration this disruption will have caused people who rely on the trains, and we sincerely apologise for that."
Work was underway to repair the fibre optics cable damaged near Papakura as quickly as possible, so normal rail services could be restored.
Mr Quinn said KiwiRail would be working to understand how the incident occurred while works was being done on installing the overhead masts and wires required to power Auckland's new electric trains.
Technical teams were also working to understand the cause of last night's signalling fault, Mr Quinn said.
"It was a local Auckland fault, and with complex equipment such as that it can take some time to pinpoint the cause."
- with NZ Herald, nzherald.co.nz, APNZ
