Prime Minister Boris Johnson has been urged to commit £39bn to Northern Powerhouse Rail (NPR) for high-speed rail links across the Pennines.
Greater Manchester Mayor Andy Burnham is one of 19 regional leaders demanding a “northern budget”.
Mr Johnson said a “very, very good case” was being made for connections between Liverpool, Manchester, Bradford and Leeds in his Tory leadership run.
He had said a trans-Pennine transport link would “turbo-charge the economy“.
The NPR project was part of Mr Johnson’s wider commitment to deliver a high-speed railway link across the north of England, which would cost about £39bn.
The leaders from the Transport for the North group are asking him to commit to the funding in full now that he is PM.
The group, which also includes mayor of the Sheffield City Region Dan Jarvis, are also demanding £7bn for road and rail projects.
Mayor of the Liverpool City Region Steve Rotheram said: “We’re consistent and focused in our plan for what infrastructure the north needs to unlock its full potential, not just for its own benefit, but for the whole UK.
“A northern budget would be the ultimate demonstration of that commitment.
“The north is clear that we only support NPR proposals that deliver the whole network, from Liverpool to Hull, along with HS2.”
Shadow chancellor John McDonnell said the investment “is exactly what’s needed and what Labour in government will deliver”.
A government spokesman said: “As the Prime Minister recently set out, this government is committed to boosting the north by levelling up our regions, through Northern Powerhouse Rail, giving local leaders greater powers and investing £3.6bn in towns across England.
“We’re already investing over £13bn in improving transport in the north – more than any government in history – and will set out our plans to build on this in due course.”