New rail services between London and Kent have been further delayed.
Thameslink services between Maidstone East and London's Blackfriars and St Pancras stations were originally due to begin last December, but were delayed for a year.
The operator and Network Rail said "a number of issues" meant services could not begin this year either.
Tom Tugendhat, Conservative MP for Tonbridge and Malling, said it was "bad news" for "long-suffering" commuters.
A joint statement from Thameslink and Network Rail, said "a number of issues have been highlighted" since the commitment to introduce services in December 2019 was made.
Services could not be launched this year "without seriously compromising reliability", the letter said.
Mr Tugendhat described the announcement as "extremely disappointing".
He said he was working with Govia Thameslink Railway (GTR) and the government to "make sure any improvements are delivered next year".
"This will at the very least help long-suffering commuters using the Maidstone East line during the key times of the day when people are travelling.
"There is no doubt that this is bad news."
No revised start date for the route has yet been given.
In May 2018 the introduction of new timetables led to chaos in large parts of the network in north and south-east England.
Fears over a repeat have led to a scaling back of subsequent timetable changes but this has delayed the launch of some new services.