The high speed rail project has already been criticised for paying more than £100 million to consultants to work on the line that will run from Birmingham to London.
And the second phase of the route - leading to the north - will see chiefs shell out up to another £150 million on consultants.
And £300 million has been budgeted for a firm that will manage all the building companies carrying out the work.
HS2 Ltd bosses say this is normal for a project of this size - but campaigners say it shows yet more money is being waste.
The line is expected to cost £50bn but critics fear that will figure will increase further.
HS2 Ltd says the project will provide a boost for businesses across the country, including smaller construction firms.
Some 84 firms from the West Midlands are in the running for £10 billion of contracts including clearing sites, planning, design, and construction.
Firms have until April 24 to express an interest with shortlisted contenders invited to bid in October.
HS2 Ltd spokesman Alastair Cowan said between £75m and £150m was estimated as the cost of consultants for phase two, and added: "They will help us put together the really detailed designs for phase two and advise us on issues like conservation.
"Things can change as we are making changes to the line as we go along."
And he said the delivery partner would be at the 'top of the pyramid' of firms involved in the construction process.
Consultants will be put on a shortlist to carry out the work rather than being given a contract.
HS2 commercial director Beth West said: "To deliver Europe's largest infrastructure project on time and on budget, we need to work closely with suppliers to ensure that sufficient planning is in place before the start of the formal procurement process.
"This will also benefit business, by giving them a head start to make the investments they require in recruitment, training and education to support the innovative ways of working we need to develop HS2."
But Stop HS2 campaign leader Joe Rukin said it was 'no wonder' so many companies wanted 'a slice of the pie when there is so much money floating about'.
He added: "It gets harder for me to keep saying this but it is unbelievable that so much money is being spent on a project that is not even close to being passed into law yet."