There is anger that a multi-billion pound project to build a railway line between Oxford and Cambridge has been classed as an England and Wales project.
The £6.6bn line will see no tracks laid in Wales, meaning the country will not benefit from extra funding.
David Chadwick, Liberal Democrat MP for Brecon, Radnor and Cwm Tawe, told Radio Wales Breakfast it was “HS2 all over again”.
The UK government said it was paid for through its “rail network enhancements pipeline, which funds projects in both England and Wales”.
Chadwick said Wales was “being denied hundreds of millions in funding that could transform our own rail network”.
He added that Labour expected people in Wales “to believe the ridiculous idea that this project will benefit them and they are justified in not giving Wales the money it needs to improve our own public transport systems”.
Unlike Northern Ireland and Scotland, most of Wales’ railway is funded by the UK government, and not ministers in Cardiff.
Under the system used to fund the devolved nations, called the Barnett Formula, Scotland and Northern Ireland get extra money when more cash is spent on rail in England and Wales.
It follows the long-standing row over HS2 – deemed to be an England and Wales project – so Wales gets no extra cash, which would be the case if it was England only.
However, none of the track planned for HS2 will reach Wales.
Differing figures have been given for how much politicians think Wales is owed from HS2, from £4bn suggested by Plaid Cyrmu and the Welsh government in the past to £350m in the most recent figures from Welsh ministers.
The UK government said its rail network enhancements pipeline also paid for the redevelopment of Cardiff Central Station, improved level crossings in north Wales and support for the upgraded south Wales relief lines.
Wales’ Transport Secretary Ken Skates said the UK and Welsh governments had agreed “an ambitious pipeline of improvements that will make up for underinvestment by previous governments” and were “seeking a fair share of investment”.
