Health Minister Edward Argar says the outline business case being developed by Shrewsbury and Telford Hospital NHS Trust should include a range of options, including that within the original costs of £312m.
But David Sandbach, former chief executive of Princess Royal Hospital in Telford, fears without the Government committing to put up more cash there will be elements of the scheme which cannot be built.
The cost of the original scheme has risen, mainly due to inflation, but Mr Argar confirmed in the House of Commons last month that £6m worth of funding had been approved 'in principle' to take the Future Fit plans forward.
Funding for the next stage of the plans had been awaited, before engaging external professionals to help complete the outline business case.
In further response to a written question from Shrewsbury MP Daniel Kawczynski over whether the Health Secretary plans to allocate £533 million to the scheme, Mr Argar said the strategic outline case should include a range of options, including within the original allocation of £312m, and will go through a 'necessary process of assurance'.
He added: "The department will continue to work closely with the trust to understand how the right support can be provided centrally, including any further early funding, to develop an affordable case for the scheme and to maximise the impact of this funding.
"Once the final full business case has been developed and approved, full funding for the build will be provided subject to the usual approval procedures."
But Mr Sandbach says it is still unclear what this means for the future.
He said: "If they only get the original budget then something can't be done.
"If they do that one would have to ask do they have to consult about that a second time?
"They consulted on a particular model which was to separate emergency away from planned care.
"It's a good idea what they want to do but if they haven't got the money to do it what are they going to do?
"If you haven't got the cash how much are you going to cut out of the scheme? If it changes substantially my view is that they would be obliged to consult on it.
"People do need to come clean about what is happening about the money."
Mr Sandbach had wanted an emergency hospital to be built to the east of Shrewsbury, which isn't the scheme that has been approved.
The approved project will see Royal Shrewsbury Hospital housing the main A&E department and consultant-led women and children’s services.
PRH will become a centre for planned care and will have a scaled-down ‘A&E Local’.
Hospital bosses say the plans will deliver safer care and better outcomes for patients, reduce cancellations of planned care and also reduce the amount of time people stay in hospital.
Sir Neil McKay, chairman of the county’s sustainability and transformation partnership, said earlier this year that discussions were ongoing with the NHS about the cost of the project.