Northampton General Hospital hopes to build new ward blocks and a paediatric and neonatal unit over the next five years, but is yet to secure funding.
The hospital, founded in 1793, has some wards from the Victorian era, plus a mix of modern buildings and others from the 1970s and 80s.
In a BBC Northampton debate, one candidate called for a new hospital.
Labour candidate Kevin McKeever said he had spoken to the trust and "they have produced a plan and the first thing to do is to rebuild kids' facilities, which are the oldest on site, and that will cost £100m".
"I also want a health and social care inquiry in Northampton to look at the health service locally," he added.
Conservative candidate David Mackintosh said: "I would be very supportive of a new hospital. I want to see improvements. You need a strong economy."
He said there would be more money for the NHS and for a new hospital if there were "more people in employment paying tax to fund the NHS".
UKIP candidate Rose Gibbins said: "I have the promise of a new hospital for Northampton as one of my main pledges. If the government can find the money for a new campus at Northampton University they can find it for a new hospital.
"People deserve better and I am sure the money can be found."
Julie Hawkins, the Green candidate, said: "We are looking at having a fully funded NHS, which is free at the point of delivery.
"We are going to take back our health service. People are not interested in how well shareholders are doing. All they want to do is see their doctor when they are ill."
Lib Dem candidate Sadik Chaudhury pulled out of the BBC Northampton debate and has yet to return calls from BBC News Online.
A full list of candidates is featured on the BBC election page for Northampton South.
Election candidates in Northampton have called for more investment in the town's hospital.