The Prime Minister has extolled the importance of the UK and Welsh governments working alongside each other during a visit to south Wales.
Sir Keir Starmer visited Taff's Well Depot on Wednesday to announce his endorsement of a pipeline of rail improvements set out by Transport for Wales, which he says he will deliver "side by side" with Welsh First Minister Eluned Morgan.
This is the first time Baroness Morgan, the Labour First Minister of Wales, has appeared alongside the Prime Minister since she offered him her support in the wake of calls for his resignation last week.
The cost of all the schemes in the pipeline is estimated at up to £14 billion, although it has not been confirmed how much additional funding will be provided as part of the UK Government's "long-term commitment" to support these projects.
Sir Keir said: "I can't overestimate how important it is to have two governments working together.
"I think many people will feel that for 14 long years, between 2010 and 2024, there was a government in Westminster which wasn't necessarily wanting to work with the Welsh government here.
"So you had a tension, looking for points of difference, whereas now we're constantly talking about how we deliver together, and that is really important for everybody in Wales, and it's the right way to do politics."
The Government has already confirmed funding towards seven new train stations in Wales, with a focus on making it easier for people to commute into Cardiff and Newport.
Transport for Wales has identified a total of 43 rail projects as part of its development pipeline, which will be prioritised for delivery.
Sir Keir added: "You've got the First Minister and the Prime Minister standing side by side to make this announcement, making absolutely clear that the commitment is there.
"We wouldn't be here announcing this if we weren't absolutely clear in the commitment to follow it through."
Last week, after Scottish Labour leader Anas Sarwar called on the Prime Minister to resign, Lady Morgan refrained from commenting until the following day.
Then, she said Sir Keir had her "full confidence", and described him as an "honourable man".
Speaking at Taff's Well Depot, Lady Morgan said the Labour Government in Westminster was setting up a vision "for the long term".
“You’ve got to stick with it, which is why stable government is crucial,” she said.
Lady Morgan added: “This is for the whole of Wales.
“This is not about the Valleys; this is not about South Wales; there is massive development planned for the whole of Wales, including rural areas.”
The announcement on Wednesday has been described as a "reheated" promise by opposition parties.
Plaid Cymru's Westminster leader, Liz Saville Roberts MP, said: "Today's announcement will feel like deja vu to many people in Wales.
(The seven new) stations were already announced in last year's spending review, with funding spread over a decade. Reheating old promises is not the generational transformation Wales was promised.
A truly transformative approach would mean fair funding, full powers over rail, and a rail strategy that serves the whole of Wales."
Welsh Liberal Democrat MP David Chadwick said: "No new funding has actually been committed today, with the Government desperately reheating old announcements to try and win votes ahead of the Senedd elections.
Sam Rowlands, a Conservative Member of the Senedd, said: "Labour cannot rewrite history - the Conservatives have consistently delivered for Wales, and this announcement fails to recognise the rail funding provided by the previous UK Conservative Government."