Wimbledon MP Stephen Hammond said he was disappointed with the news the Northern line is to be permanently spilt.
All trains to and from Morden will travel via Bank and London Bridge. Passengers wishing to travel using the Charing Cross branch would have to change at Kennington.
Mr Hammond said: “These passengers will not welcome the news they no longer have direct access to the West End.”
The number of trains on both stretches of the line are to be increased to tackle overcrowding.
The changes are due to be completed by 2018.
Mr Hammond said: “I am disappointed my campaign to prevent the split of the line at Kennington has not been successful.
"Improving transport links to and from the Wimbledon area will continue to be one of my priorities for the next Parliament.”
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