There are currently approximately 40,000 - 50,000 nurse vacancies in England.
I don't suppose that pay is the only reason that there are vacancies, but it's naive to think it doesn't play a part.
If you look at the long-term plans for the NHS, it's clear that nurses are expected to take on an increasingly specialist role, including work which is currently carried out by doctors, who take much longer to train and at greater cost.
If the plans succeed, the idea is that there would be efficiency savings and productivity and value for money would increase, but it's a big IF. The plans won't work, unless there are sufficient well-trained nurses.
In addition to the arguments about fairness of nurses' pay, it seems to me that there's a pragmatic argument. Unless there's investment in nurses' pay, training and working conditions (as well as infrastructure improvement), the NHS stands little chance of standing still, never mind improving.