Plaid Cymru leader Rhun ap Iorwerth has said the Welsh Labour government needs to secure fair funding for Wales – including for HS2 high speed rail – before his party would consider supporting its budget.
But he said he had not heard a “whisper” that was happening, accusing Labour’s Welsh government of “given up on standing up for Wales” to avoid embarrassing Prime Minister Sir Keir Starmer.
Labour needs the backing of at least one other party to get its spending plans through the Senedd.
His comments came on the second day of his party’s conference in Cardiff.
Plaid Cymru wanted to use the event at the Principality Stadium to look ahead to the 2026 Senedd election, portraying itself as a government in waiting.
Its leader had told party members that the vote will be a real chance to change Wales.
But the event was marred by a row over the initial refusal of the leader of Gwynedd’s council to apologise to the victims of the paedophile headteacher Neil Foden, which led to the resignation of four of his cabinet members.
Dyfrig Siencyn has been under pressure to quit since his interview with Newyddion S4C. He reversed his stance and apologised in a statement from Cyngor Gwynedd a day later.
Meanwhile party members backed a motion to call for a boycott of Israel over the war in Gaza.
Labour has 30 seats in the Senedd and needs the help of at least one opposition politician to get its spending plans agreed. That usually means Labour ministers have to strike a deal.
Plaid Cymru argues that Wales should be funded through a needs-based formula, and not the Barnett system, which is based on population.
Ap Iorwerth criticised the Welsh government for its recent £350m assessment of how much it thinks is owed to Wales from the High Speed 2 (HS2) line. Ministers had argued in the past that it was worth billions.
The project is designated an England and Wales scheme, meaning the Welsh government receives no additional cash as a result, despite none of the railway reaching Wales.
“Welsh government isn’t even asking now for what Wales is owed, and that tells you everything you need to know about the way Labour in power in Wales is short-changing Wales,” said ap Iorwerth.
“They call it a partnership in power, something that will deliver for Wales.
“So if they want to come to the table and say we can deliver on HS2 funding and fair funding and on devolution of powers over the Crown Estate, let’s talk.
“I’m not seeing any whisper that that’s happening.”
‘Get to work from day one’
Welsh government ministers have been making the case to their Labour colleagues in the UK government for increased railway funding.
At the Council of Nations and Regions on Friday, First Minister Eluned Morgan said she did not expect to see extra money for HS2 in Chancellor Rachel Reeves’s budget this month.
“We need more time for that,” she said.
Separately on Saturday, Plaid Cymru Member of the Senedd (MS) Luke Fletcher set out the party’s plans to grow the Welsh economy.
He said a Plaid Cymru government would establish a new national development agency, reform Wales’ development bank, and reform business rates for small and medium-sized businesses.
He said: “A Plaid Cymru government will get to work, from day one, on fixing those vital foundations of our economy.”
The full interview with Rhun ap Iorwerth can be seen on BBC Politics Wales at 10:00 BST on Sunday 13 October, or on iPlayer after broadcast.