THE SNP MP Dr Lisa Cameron has left the party and joined the Conservatives.
She told The Daily Mail her decision was motivated by a lack of support shown by the party towards her mental wellbeing.
She claimed she was shunned by other SNP MPs at Westminster after challenging the support given to former chief whip Patrick Grady, who was suspended from the House of Commons and apologised in Parliament after being found to have acted inappropriately towards a party staffer.
She said: "I do not feel able to continue in what I have experienced as a toxic and bullying SNP Westminster group, which resulted in my requiring counselling for a period of 12 months in Parliament and caused significant deterioration in my health and wellbeing as assessed by my GP including the need for antidepressants.
"I will never regret my actions in standing up for a victim of abuse at the hands of an SNP MP last year, but I have no faith remaining in a party whose leadership supported the perpetrator's interests over that of the victims and who have shown little to no interest in acknowledging or addressing the impact.
"It is also true that I have received no contact from party leadership in the past weeks, despite members of every other main political party contacting me to offer support and compassion during what has been an extremely difficult time.
"I am particularly grateful to the Prime Minister in valuing my continued contribution to Parliament as a health professional and in taking time to listen. It is the first time I have felt heard and shows positive, inclusive leadership in contrast to that which I have encountered in the SNP at Westminster over many years."
The MP also appears to have had a significant change of heart about independence, saying she will now focus on "constructive policies that benefit everyone across the four nations of the UK".
She added: "Families like mine experienced significant division regarding the issue of independence.
"This has taken its toll and I have come to the conclusion that it is more helpful to focus my energies upon constructive policies that benefit everyone across the four nations of the UK, and to move towards healing these divisions for the collective good.
"Being in the SNP has been bad for my health. I will be taking time as advised to recuperate and will continue as always to focus upon serving my constituents.
"Thank you to everyone who has reached out to me who wishes to see a politics where victim blaming, and abuse is never tolerated."
The decision comes just hours before Cameron was likely to be deselected as an SNP candidate at the next General Election.
She had reportedly threatened to take legal action against the party over the selection process. Scottish Government minister Christina McKelvie announced her support for a different candidate, Grant Costello, last month.
