Five Crossrail stations are to be delayed, according to reports.
West Ealing, Southall, Ealing Broadway, Acton & Hayes & Harlington, which were due to be built by the end of this year have been put back to 2019, the BBC has reported.
A spokesperson for Crossrail, named the Elizabeth line, said: “Network Rail is a key partner in delivering the Crossrail project and is upgrading the existing railway in west London in preparation for Elizabeth line services.
"Network Rail’s planned works will deliver the station upgrades at Acton Main Line, Ealing Broadway, West Ealing, Southall and Hayes & Harlington by December 2019 when Elizabeth line through services commence from Reading, Maidenhead and Heathrow.”
The timeline for the introduction of the Elizabeth line is on track, said Ben Wheeldon, programme director for Crossrail at Network Rail.
"Network Rail has already delivered extensive infrastructure upgrades to enable the introduction of the Elizabeth line, and by December this year we will have completed all of the rail infrastructure in Ealing needed to support the testing of Elizabeth line trains in advance of their introduction next May," he said.
"The new station building and accessible pedestrian footbridge will be completed by December 2019, which is when the Crossrail project completes and the full Elizabeth line services are introduced, linking Ealing with central London.
"As a result of Crossrail construction work for the Elizabeth line, passengers and residents in Ealing are already seeing real improvements to their railway and train service. The electrification of the line to Maidenhead and a new lengthened bay platform at Hayes and Harlington has facilitated the introduction of GWR electric services to Paddington, providing over 1,000 seats into Paddington at the busiest times."
The first Elizabeth line trains entered passenger service last week. A train running between Liverpool Street Main Line and Shenfield set off on its first trip after eight years of construction work.
The first Elizabeth Line train was initially due to enter passenger service between Liverpool Street Main Line and Shenfield by the end of May, but it was pushed back until this month as thorough testing of the train needed to be completed.