Dr Beverly Malone, a former aide to US president Bill Clinton, was brought in just over a year ago - the first overseas general secretary in the organisation's history.
Her salary package was also unprecedented - £200,000 in the first year, including relocation expenses from the US.
Now she is being accused of marginalising the Scots and Welsh arms of the RCN in a reorganisation, and attending a Labour Party fundraiser despite the organisation's fiercely non-political stance.
Former president Dame June Clark told the BBC: "I think there are some quite serious errors of judgement going on at the moment."
The reshaping of the RCN involved giving Wales and Scotland the same status as English regions.
Dame June said: "I think that Beverly Malone misread the British culture and in particular what political devolution means."
She also labelled Dr Malone's attendance at the fundraiser as an "error of judgement".
"It was an incredibly naive thing to do and it means that either she is being poorly advised by the people around her or she is not listening to the advice she gets."
Dr Malone says that she was invited to the fundraiser by a third party, and contributed nothing to Labour Party funds.
Non-urgent operation
However, further criticism has been levelled over the general secretary's mother, Dorothy Malone, who, despite being a US citizen, received a non-urgent cataract operation on the NHS at a London Hospital.
This is not illegal - if Dorothy Malone were applying for permanent residency then she would be entitled to free treatment - but has nevertheless caused disquiet among some RCN members.
Professor Ray Rowden, who has held many posts in the RCN, said: "I think a lot of nurses will look at this and say, a woman who allegedly received £200,000 last year, why didn't she pay for her mother's surgery - and can it be right for a foreign national who has paid no tax or national insurance to access the NHS in this way?"
Now a petition is being organised calling for the college council to explain what has been going on - and if it fails to do so the campaigners say they will attempt to trigger an extraordinary general meeting with a vote of no confidence in Dr Malone.
Dame Betty Kershaw, another RCN stalwart, said: "My advice to the council would be that they themselves should offer the opportunity to have an extraordinary general meeting.
"That would give the opportunity in private for members to raise the concerns that they very obviously have."
Stout defence
The Royal College of Nursing issued a detailed statement on the criticisms of Dr Malone.
It said: "The general secretary's salary is set in the same way as other senior executives at the RCN.
It is discussed by the RCN's remuneration committee who make a recommendation to its council - the governing body of elected RCN members - for a final decision."
On the fundraiser, it said: "Dr Malone was invited to this event by a third party.
"She attended for the early part of the reception and then left before dinner. No donation was made by her.
"The RCN is politically impartial and seeks to raise nursing and patient issues with all major political parties across the UK." The college said Dr Malone's mother had the same rights to patient confidentiality as any other NHS patient.
It added: "Dr Malone's mother is living in the UK and has received treatment under normal guidelines relating to NHS treatment."
The statement defended the reorganisation of the college, saying that its aim was to achieve "better services" for members.