A temporary timetable has been introduced on South Western Railway due to staff shortages because of the Omicron variant of Covid-19.
From Monday 17 January, there will no longer be direct trains from Weymouth to London.
Passengers travelling from Weymouth towards Southampton and London will have to change at Bournemouth.
Key timetable changes include:
Waterloo to Exeter services will split at Salisbury
Waterloo to Weymouth services will split at Bournemouth
The Shepperton branch will reduce to hourly
Waterloo to Alton will reduce to hourly
Waterloo to Basingstoke will reduce to hourly
The last train of each day will be earlier than at present
The company said the spread of Omicron has "necessitated the need for a new timetable" to "ensure reliability for customers" and "cater to key workers, school pupils and those who cannot work from home".
It added that the changes will remain "under review".
Passengers are being urged to check their journey before they travel here.
Claire Mann, Managing Director, South Western Railway said: "The spread of the Omicron variant has had a significant impact on our railway, with fewer people using the train and staff shortages impacting on our ability to consistently deliver the current timetable.
"Having assessed demand and spoken to our industry colleagues, we believe this new timetable is the most effective means of ensuring our customers receive a reliable service, with short-notice cancellations minimised.
"Journey planners will be updated on a week-by-week basis, with updates taking place towards the end of each week. Customers should check their journey as close to their time of travel as possible."