Network Rail, MPs and Birmingham City Council have promised a united front in the campaign to convince the Government to rebuild New Street.
But the pledge followed a period of difficult negotiations between the rail operator and politicians.
MPs were not convinced Network Rail had drawn up a business case capable of convincing the Government.
But the rail operator has now delivered a report on rail capacity in the West Midlands to the Department for Transport which has been agreed with MPs.
And it plans to submit a planning application in the middle of August.
As part of the new united campaign, a delegation of city MPs yesterday met Transport Minister Derek Twigg in the House of Commons, to urge him to back the £500 million "Birmingham Gateway" development.
The cost of New Street's refurbishment to the taxpayer will be £350 million, with the rest coming from the private sector.
MP Gisela Stuart (Lab Edgbaston), who is leading a cross-party campaign to back New Street, said: "The city's MPs have quite rightly been asking a lot of questions about the proposals.
"Much of the discussion has focused on the issue of future rail capacity and ensuring that future increases in passenger numbers can be managed.
"We are now satisfied that the Gateway proposals are the best way forward."
She said: "We believe the Government is already keen to help fund the project and we will be urging Ministers to ensure there is no delay in taking it forward."
Network Rail's programme director Martin Chambers added: "We are especially pleased that the MPs have taken the time to look so closely at our plans on rail capacity."
Coun Mike Whitby, leader of Birmingham City Council, said: "I am delighted by the serious approach taken to this issue by the city's MPs.
"The redevelopment of New Street is a top priority for the council."
Jerry Blackett, of Birmingham Chamber of Commerce and chair of the West Midlands Business Transport Group, said: "It is vital that we all speak as one on the importance of this project to Birmingham."
MPs were concerned Network Rail had failed to explain clearly why the redevelopment of New Street was needed, given that proposals to increase rail capacity in the region by upgrading track may not go ahead.
They also demanded that Network Rail commit itself unambiguously to the Gateway project.
The rail operator is also looking at the possibility of a new Birmingham "Grand Central" station, but this would be in addition to New Street.
A refurbished New Street will include a larger passenger area at New Street, relieving the congestion that has in the past led to the closure of the station.
The project will also include redeveloping the surrounding area and providing better pedestrian connections across the city centre.