The comments come in response to new figures published by the Nursing and Midwifery Council (NMC) that show an increase in the number of nurses and midwives leaving the register, while at the same time, numbers joining have slowed down.
This has resulted in an overall reduction in the numbers of nurses and midwives registered to work in the UK.
Janet Davies, RCN Chief Executive & General Secretary, said: “These figures are the starkest warning yet that nurses have put up with too much for too long. Our members have had enough, and as a result the profession is shrinking.
"With more people leaving than joining, the NHS will be further than ever from filling the 40,000 vacant nurse jobs in England alone."
The average nurse is £3,000 worse off in real-terms compared to 2010. The 1% cap means nursing staff can no longer afford to stay in the profession and scrapping student funding means people can no longer afford to join it.
Janet added: “Just as worrying is the fact that these latest figures show more British nurses are moving to work abroad. Theresa May can't wait months to lift the pay cap and bring people into nursing. She must concern herself with reversing this trend immediately.”