The electrification of the Lakes Line - linking Oxenholme and Windermere, has been pushed back - and might not happen until as late as 2024.
It had been due to be electrified by next year, after a £16 million investment package was announced by the last coalition government.
But a new report shows that the work has been pushed back into what's called ‘Control Period 6’, meaning it might not happen for another eight years.
Local MP Tim Farron has written to the Transport Minister to set out the case for the electrification of the Lakes Line, and urge him to press ahead with the work.
He said: “The electrification of the Lakes Line is an important infrastructure upgrade which will provide a real boost to the local area. It makes economic and environmental sense, and will enable the line to be better integrated with the main line and routes to Manchester Airport.
“There is a sense of déjà vu in once more making the case for this to happen – it was given the go-ahead by the Lib Dems in government, but has now been delayed by the Conservatives. Once again, much-needed infrastructure investment in our area is being overlooked by the current Conservative government, but I will continue to campaign for this.”