There will be no rail services on the London Waterloo to Alton and Portsmouth lines on Saturday (September 30) and Wednesday, October 4 because of strike action by train drivers.

An overtime ban by members of the ASLEF union will also affect the South Western Railway (SWR) network tomorrow (Friday) and October 2, 3, 5 and 6. But unlike on the Saturday and October 4 strike days, the operator hopes to run a normal weekday timetable with only a small number of cancellations on these days.

Journey planners for tomorrow and Saturday, and October 2 and 3, are up to date. Journey planners for October 5 and 6 will be updated in “due course”. See www.southwesternrailway.com

Customers are advised to travel only if absolutely necessary on strike days. If customers must travel, they should check their entire journey before travelling, as other operators will also be affected.

Stuart Meek, SWR’s chief operating officer, said: “I’m sorry to say that, because of industrial and strike action by the ASLEF union over the next two weeks, we will be forced to make changes to our timetables.

“We’re very sorry for the disruption this will cause and we’re very grateful to our customers for their continued patience.”

Transport secretary Mark Harper has described the latest strikes as “cynical” and “politically motivated” as they clash with the Conservative Party conference in Manchester from October 1 to 4.

The train drivers’ union ASLEF and the RMT union have been locked in a row with train companies over pay and working conditions for the past 18 months, leading to a succession of strikes and rail cancellations.