CBI chairs in six English regions including the West Midlands have issued a joint statement insisting that HS2 is built in its entirety, describing it as "vital to the UK’s future prosperity".
It comes as speculation mounted that at least part of the route could be scrapped, with the findings of an independent review into its future due at the end of the week.
Phase One of HS2 is due to run from London to Birmingham, with subsequent phases including a route through Staffordshire to the north west.
Boris Johnson instructed former HS2 Ltd chair Douglas Oakervee to look into the line over concerns about its cost, which critics warn could be almost double its £55 billion budget.
The CBI statement says: "Businesses need HS2 to be built in its entirety, linking the east and west of the country as well as bringing the north and Midlands closer together."
It was signed by regional chairs from theWest Midlands, East Midlands, Yorkshire and Humber, London, the North East, and the North West.
CBI regional director Richard Butler, said: “HS2 is more than just a railway line, it’s a key that unlocks future jobs, training and regeneration opportunities that will benefit us all.
“We have all come together to make a joint intervention in this debate, we believe that HS2 is crucial in supporting the UK government aim of rebalancing the UK economy and boosting productivity in the regions.
“It is time for MPs and policymakers to lift their gaze, put the national interest first and back HS2.
"We cannot have more dither or delay. Britain needs to be bold and I am urging them to back HS2.”
Around £7 billion has been spent on HS2 so far. The first phase is due to open in 2026, although last month ministers announced it could be delayed by up to five years.
Addressing concerns that the project could be downsized, the statement says: "A scaled back version of HS2 will not deliver the improved connectivity across the country that businesses are crying out for."
The CBI says HS2 will create half a million jobs, stimulate house-building along its route and support investment across the Midlands and the north.
CBI chief UK policy director Matthew Fell, said: “Any watering down or cutting of this critical scheme will threaten the massive benefits of the scheme. It is time to be bold and deliver this scheme in full.”