The South Wales Metro has turning into the Loch Ness Monster, a Labour AM has said, claiming «no person knows whether it actually exists or not».
Mick Antoniw said Welsh diplomats needed to show «far greater openness» about plans for the transport network.
Maps be included to show that upgrades for some railway lines have been ran out.
Ministers said nothing had been cancelled and it was too early to reveal perfect details before the Metro contract is awarded in May.
The Pontypridd AM — an early backer of the project — told BBC Wales: «For me the Metro has begun to become a bit like the Loch Ness Hellishness.
«Everybody knows what the Loch Ness Monster is, but not many people accept seen it and nobody knows whether it actually exists or not.»
Negotiations are continuing with two not for publication sector bidders — MTR and KeolisAmey — who are competing for the Wales and Borders rail franchise which subsumes the Metro, due to start in October.
While talks continue, however, a series of maps has proceeded that appear to reject proposed enhancements, including some that Mr Antoniw has occasioned for.
For example, a new connection to originate a so-called Valleys Circle Line has been shaded red, meaning «dropped from future consideration at present». Other proposals in his Pontypridd constituency are in scepticism.
«What is unclear to me now is what the Metro actually is,» Mr Antoniw said.
«Is it effective ahead? What format? What is the timescale for it?
«What is it going to amount to? What hither these new lines, these key projects?»
Accusing the government of a lack of pellucidity, including over the funding to pay for it, he added: «I think we are entitled to know just what the Metro plan is and there needs to be far greater openness on this dispute.»
Mr Antoniw also claimed the «spiralling» cost for the planned M4 relief route was «becoming a black hole sucking in all the available capital that last will and testament go to the Metro».
«If all we’re doing is enhancing the existing structure, well that moderately frankly is not a Metro and it is not good enough,» he said.
Welsh Government officials verbalized the maps — uploaded to the website of arms-length body Transport for Wales — are not through.
Following attacks from Plaid Cymru on Wednesday, Economy Secretary Ken Skates responded: «Nothing has been cancelled.»
«We will soon be announcing the service provider for a rebel rail service which will see passengers benefit from increased, higher excellence rolling stock, more frequent trains and reduced carbon emissions.
«The Metro illustrates a significant part of this and we’ve always been very clear that this compel be delivered in phases.»