An MP says it would be "a bizarre decision" if the franchise to run most Sussex trains was awarded to the current operator.
Eastbourne MP Nigel Waterson is calling on rail authority bosses not to award the South Central rail franchise to Connex.
A decision on the franchise is expected to be announced on October 25.
Connex is bidding against GoVia, which currently runs the Thameslink service from Brighton to London.
Mr Waterson said: "I believe I can speak for the vast majority of my constituents when I say that a decision to award the next franchise for our area to Connex would be a bizarre decision as well as being extremely unpopular.
"In recent times Connex has become a byword for poor punctuality, slovenly rolling stock, poor service and insensitivity to consumer complaints. It is high time they were replaced."
The Conservative MP recently met bosses from Connex and GoVia, along with senior Eastbourne councillors.
Mr Waterson said: "I have little doubt that the GoVia bid would provide a better service for my constituents that that presently offered by Connex. Any other decision would be a major disappointment."
Town chiefs are anxious to see rail services improve as part of the local transport plan and to boost tourism.
A Connex spokeswoman said: "We have been working very hard with the existing infrastructure and rolling stock to deliver the best rail service we possibly can.
"After our meeting Mr Waterson went away fully understanding the limitations of the current infrastructure.
"If Connex was no longer running South Central it is unlikely that there would be a significant change in service in the short or medium term."
Connex says it needs more time to improve the Victorian-built railways and trains which date back to the Sixties.
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