Eight additional Arterio trains have been launched in the past two months, bringing the total in operation to 14 across over 160 weekday services.
Labour MP Fleur Anderson campaigned on the issue, highlighting 'extreme overcrowding' on lines approaching Waterloo, particularly in areas like Wandsworth Town.
The new trains, described as 'platform hoovers', are designed to carry over 50 per cent more passengers and offer modern amenities like Wi-Fi and charging points.
The full rollout of the £1 billion Arterio fleet was significantly delayed, with the first trains only carrying passengers in January 2024, reportedly due to driver training issues.