The comments were made in response to a report from the Communities and Local Government select committee, which showed the turnover rate for nurses working in social care is 35.9%.
The report said the Government needs to urgently review how social care is funded in the long term and address serious threats to social care provision.
It also called for better pay, terms and conditions for staff as well as a clear development pathway.
The RCN said social care had suffered from high turnover rates and underfunding for too long.
RCN Employment Relations Adviser Clare Jacobs said: “Despite playing a critical role in delivering care, nurses and care assistants have been repeatedly undervalued, so it’s no wonder they are choosing alternate careers.
“The Committee highlights low pay, low status and lack of future progression as serious challenges in maintaining the social care workforce.
“The Government should heed the Committee’s warnings and put in place robust and long-term workforce planning arrangements to ensure we have enough care staff.”
Clare also said all care staff should be registered to support training and raise standards.