Former chancellor George Osborne has said that Theresa May had a "wobble" over his Northern Powerhouse project after she became Prime Minister.
Osborne's comment, as he launched a new think-tank to drive the scheme forward, is the clearest indication yet that he had to fight to keep his flagship policy on track after being sacked from the Government in July.
He announced that he has recruited the former mayor of New York, billionaire businessman Michael Bloomberg, to advise the powerful new elected "metro" mayors being created in city regions including Manchester, Liverpool and Sheffield.
Osborne will chair the Northern Powerhouse Partnership, an independent group, including politicians and business leaders, to help push the agenda of greater powers and investment for the regions to boost jobs and growth.
The future of the initiative, launched by Mr Osborne in 2014, came under question after Mrs May's arrival in 10 Downing Street in July.
She initially appeared reluctant to use the phrase "Northern Powerhouse", speaking instead of a broader nationwide industrial strategy, rather than a regional focus solely on the north.
Osborne told BBC Radio 4´s Today programme: "I think, to be honest, there was a little bit of a wobble when we had the new administration about whether they were still committed to the concept of the Northern Powerhouse."
He added: "I'm the first to say we need economic development across the whole of the country. I sweated blood to get a mayor for Birmingham. That was one of the most difficult things I pulled off in office. I'm passionate about building out the engine of the West Midlands.
"But in the North of England, there is a particular opportunity because the cities are close together."
Plans included new investment in north-south high-speed rail, HS2, and an east-west version, HS3, linking the belt of northern cities from Liverpool to Hull, via Manchester and Leeds.
The plans also included the election of 'metro' mayors for bigger city regions, including for Manchester, Liverpool and Sheffield.
But Andy Burnham and Steve Rotheram, both MPs and Labour's candidates for the mayoral elections in Manchester and Liverpool, recently warned Mrs May that pulling the plug on the "Northern Powerhouse" agenda would be "as big a betrayal as the 1980s when Margaret Thatcher pulled the plug on our industries".
Osborne insisted: "The Northern Powerhouse is here to stay."