Govia Thameslink Railway (GTR) defended its decision to launch its new timetable last month despite uproar over severe delays and cancellations.

The London Assembly transport committee grilled rail chiefs from GTR and Network Rail over the new timetable which was introduced on May 20 – just three weeks after it was finalised.

The time of every train on the GTR network (Thameslink, Southern, Great Northern and Gatwick Express services) was changed to make “improvements” – but this led to chaos amongst passengers who had to battle through severe delays and cancellations.

Conservative assembly member Keith Prince was the first to question rail chiefs on why GTR had gone ahead with timetable changes, when they were only finalised three weeks before the new timetable launch date.Mr Prince said: “The industry standard says that the timetable should be ready 20 to 21 weeks before it is launched. Could you not have delayed it for at least 15 weeks?”

John Halsall, route managing director for Network Rail in south east England said: “With three weeks to go we weren’t waving the red flag.”

Labour party assembly member, Tom Copley, was quick to join the debate, asking: “With only three weeks to go you should have known whether or not the timetable was going to work, how on earth wasn’t a red flag going up then?”

“In hindsight do you think it was the wrong decision to press ahead with the planned changes?”

But Nick Brown, chief operating officer for GTR insisted that more drivers had been brought in to make sure that the timetable would run as planned.

He said: “The number of drivers we had was actually greater than we needed.”

GTR said they needed 889 drivers for the timetable changes to go ahead but at the time had 898.

But Mr Halsall revealed that the extra drivers had been recruited because many did not know the routes for the new timetable and needed extra driver training.

Liberal Democrat assembly member Caroline Pidgeon raised her concerns about the lack of properly trained drivers which had led to numerous delays and cancellations since the new timetables were launched.

Ms Pidgeon said: “Last November we were told that it was too late to start training drivers for the new timetable launch.”

Mr Halsall dismissed her claims as a problem, saying: “We were satisfied that we had enough drivers and we knew we were going to have to continue training drivers after the new timetable was launched.

“I think everyone will agree that the planned changes we have are ambitious, but they will work.”

It was Labour assembly member, Florence Eshalomi who finished the discussion stressing the problems passengers now faced.

Ms Eshalomi said: “A Which survey revealed that three out of five respondents said that these new timetable changes are impacting upon their health and in turn they are taking that out on hard-working train staff.

“What is your message to passengers?”

Mr Brown told the assembly: “We know and feel the discomfort of passengers and the impact this is having on people.”

He also said that GTR was responding to compensation claims for delayed or cancelled services.