Expansion of the DART around Dublin is going cost €600 million more than expected.

The Dart expansion project was allocated €2 billion when it was developed under the National Development Plan, to run from 2018 to 2027.

The project aims to connect electrified rail services from Dublin city centre to areas such as Drogheda, Maynooth and Celbridge.

But new estimates from Irish Rail are putting the final cost for the project at €2.6 billion, according to latest figures.

Other risks have been noted that could increase the growing costs further.

For example, relocating the Docklands rail station to Spencer Dock could add another €100 million to the final costs.

While the DART expansion project is still largely at the planning phase, the expected costs have risen rapidly from the original estimate.

The cost of inflation during the project has also increased in the project calculations, the Irish Times reports.

The CIE, the State-owned transport group, told Minister for Transport Shane Ross that “the amount of money earmarked for public transport initiatives in the National Development Plan may not be sufficient to fund the full scope of work envisaged on those projects”.

The full scope of the overrun has only emerged today according to The Irish Times.

The project costs have risen by more than €200 million since last May.