Thameslink and Great Northern rail services are set to be affected by industrial action from Monday (July 17).
Passengers have been advised to check every journey until the end of July, despite strikes ending on Saturday, July 29.
Services from Monday until the end of July are "likely to be busy", with customers potentially having to queue or even miss their usual train.
READ MORE
- Bim Afolami raises plight of first-time buyers at PMQs
- Essex & Herts Air Ambulance celebrates 25th birthday with 'thank-a-thon'
A nationwide ban on overtime has been put in place by the ASLEF union from Monday, July 17, until Saturday, July 22.
National strike action by the RMT union will also take place on July 20, July 22 and July 29.
Separate industrial action will also take place on the London Underground between Sunday, July 23, and Friday, July 28.
Get more stories like this delivered to your inbox every week by signing up to our newsletter.
Chris Fowler, head of network operations for Govia Thameslink Railway, said: “We’re really sorry about the impact that this round of industrial action will have on our customers, especially as many will be looking to start their summer holidays.
"Where possible, we’re running as many trains as we can, but unfortunately there will be some days and times where people will be left without a service.
"It’s incredibly important that people check every journey they plan to make before they travel and leave plenty of time, as our services will be much busier during this period.”
Journeys can be checked via the National Rail website: www.nationalrail.co.uk
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here