The NHS risks a shortage of nurses if it shirks hard choices, the Health Secretary has said, as students protest against the Government's decision to scrap nursing bursaries.

Jeremy Hunt said the decision to replace bursaries with loans in 2017 had to be taken for financial reasons and, if done "right", could see up to 20,000 more nursing posts in place by 2020.

Student nurses and midwives gathered outside the Department of Health today to rally against the move, announced by Chancellor George Osborne last week.

The plan was unveiled in the Comprehensive Spending Review and is expected to free up around £800 million a year in Government spending.

The measure has been heavily criticised by unions including Unison and the Royal College of Nursing (RCN), which described it as "a crushing blow".

Mr Hunt, addressing senior nurses from across healthcare in Birmingham, said: "The big mistake would be to duck difficult decisions and have a shortage of nurses in five years."

Speaking at the Chief Nursing Officer for England's annual conference, he told delegates the cut was needed as part of measures to relieve "enormous pressure on hospital finances" and pay for other measures in the health service.

He said: "In order to do those things and, very bluntly in order to fund those things, we've had to take difficult decisions on tuition fees on bursaries."

Mr Hunt added: "I think we do have to recognise the system we have at the moment is not working."

He said the NHS was grappling with "huge vacancy rates" in nursing, while a third of roles were filled by nurses recruited from overseas.

"Other posts are filled by expensive agency nurses, putting enormous press on hospital finances," he went on.

"We have a problem and being blunt I don't want to make the mistake of five years ago where nurse training places were cut, when we know we'll need more nurses - there isn't a part of NHS that doesn't want to employ more nurses."

Mr Hunt said he would listen to student nurses and work with the RCN and unions over the changes.

"If we get this right we can see a possibility of 10% increase in nurse training places this Parliament compared to the last, and 15% increase in nurse degree places and according to Health Education England they have projected 20,000 more nurses in post this Parliament."

He said the move could lead to better nursing care for patients and described the measure as "the right thing to do".

Mr Hunt also added that the changes could lead to an increase in more nurses from poorer backgrounds, although unions have said the measures would have the opposite effect.

Janet Davies, chief executive of the RCN, said: "The Chancellor's move to axe our bursaries is a crushing blow."

She added: "Bursaries aren't a luxury, they're a lifeline. Our students don't apply to study nursing, they apply to train to be a nurse."

Ms Davies went on: "Bursaries are crucial and all this will do is deter prospective nurses from applying. Given the serious nursing shortage this will further damage what is already a very fragile NHS."

Critics of the changes have said student nurses, midwives, occupational therapists, speech and language therapists, podiatrists and radiographers would all face graduation with thousands of pounds of debt.

Unison said its calculations showed a student graduating in 2020 could leave with debts of more than £50,000, but will start on a salary of less than £23,000.

The union's general secretary Dave Prentis said: "There's a shortage of nurses because the coalition severely cut the number of training places. It's hard to see how scrapping the bursary will do anything other than make what is already a difficult situation much worse.

He added: "Our NHS needs to attract nurses from every walk of life. Removing the current level of financial support means many would-be students will be forced to abandon their dreams of becoming nurses, midwives, radiographers and occupational therapists."