Electrification means UK ministers cannot be trusted, says Jones
The UK government cannot be trusted on Brexit after it cancelled a planned upgrade of the railways for Swansea, First Minister Carwyn Jones has said.
Whitehall had tried to "sideline" Wales, he said, pointing to a decision to stop electrification beyond Cardiff.
His comments came ahead of a meeting to discuss Brexit with Scottish First Minister Nicola Sturgeon in Edinburgh.
Talks between the Welsh and UK governments are due to happen in September.
But Mr Jones said that "so far they have refused to speak to us or Northern Ireland or Scotland."
First Secretary of State Damian Green met Scotland's Brexit Minister Michael Russell in Edinburgh last August, but the talks resulted in no agreement.
UK ministers have said the devolved administrations will not lose any powers as a result of withdrawing from the EU.
Under the plans for the UK government's repeal bill, powers returning from Brussels would be held in Westminster until new rules - on things such as farm subsidies - are agreed between the UK and devolved nations.
However the Welsh Government has described the plans as a "power grab" - and Mr Jones said he did not believe assurances that powers would only remain in London temporarily.
On Tuesday, he Scottish and Welsh governments agreed to propose changes to that bill.
'Flying out the window'
"Why should I believe a UK government that told us it would electrify the mainline to Swansea? That went flying out the window," Mr Jones told BBC Radio Wales' Good Morning Wales programme.
"Unfortunately no, I don't believe the UK government on this."
There needed to be a "common way forward" between the "partnership of four nations", he said.
The Welsh Labour leader also denied there was a rift between him and Jeremy Corbyn over the best deal for Britain.
He said Mr Corbyn shared his view that the UK should retain as much access as possible to the European single market, without trade tariffs.
"We're in pretty much the same position," he said.
The UK government played down notions of a rift with the Welsh government, with one source calling the first minister's comments "frustrating".
Senior officials on both sides were talking to each other on a daily basis behind the scenes, the source said.
Prior to Mr Jones's comments, a UK government spokeswoman said: "It is our expectation that the outcome of this process will provide greater decision-making power for each devolved administration and we are committed to positive and productive discussions going forward."
Welsh Conservative leader Andrew RT Davies, dubbed Mr Jones's meeting in Scotland an "unhelpful sideshow", which he said was "just the latest in a long line of attempts by Carwyn Jones to undermine Brexit".