Passengers travelling on South West Trains during off-peak hours are to see train carriage cuts, according to a leaked memo.
The train company, which runs services throughout the borough, said it has made the decision to run nearly 200 shorter trains a day to save money.
But SWT spokeswoman insisted the decision will not affect rush hour trains and will only impact on daytimes and weekend services.
She said the decision was made based on 'new technology" which allows them to accurately monitor how many passengers they are carrying.
"It will save us money as even though the trains are electric we still have to pay for that electricity," she added. "Hopefully people will not even notice the changes."
The e-mail, which was leaked to the BBC, read: "Most changes relate to our need to control costs, which has resulted in a number of train formation changes. Some of those concerned are already in place on a STP (short term plan) basis, but will now become permanent."
The programme is said to have already started but will roll out fully in the next few weeks.
Last week it was announced that another cost-cutting plan to reduce ticket office opening times at stations like Brentford was thwarted by transport chiefs, who rejected many of the changes to 'protect passengers'.