Collins, a financial services comms specialist who has 24 years' experience in PR, resigned some time ago but has stayed in the role until the recruitment of Jamie Brookes from BNY Mellon as MHP MD. He started at the Engine-owned company last month.
Collins has held her current position since MHP was formed in 2010 via the merger of Penrose Financial, which Collins co-founded in 1998, with Mandate Communications and Hogarth PR.
"It was a difficult decision but it’s something I’ve been thinking about for a while," said Collins, who is also a founder steering committee member of the 30% Club, which aims to increase representation of women on UK boards, and a non-executive director of JP Morgan Overseas Investment Trust.
"I have a very full-time full-time job, and I have my 30% Club role and my JP Morgan Overseas non-exec role, and I just decided it was time to take a step back, decide what I want to do - it’s very difficult to do that when you have a full-time role with lots of clients.
"It was a tough decision because I’ve loved MHP, but when I sold [Penrose] I had to stay for two years, and it's now four-and-a-half years. I just felt I needed to clear my head a bit and decide what to do next."
Collins told PRWeek she had been offered a consultancy role within MHP. "I haven’t decided whether to accept it or not," she said. "I just don’t want to make any decisions for a few weeks. I’m going to have my first holiday without being tied to a BlackBerry."
Asked if she would set up a new agency, Collins said: "I really have no idea."
A spokesperson from MHP confirmed Collins' departure and said: "She remains a close friend of the firm and we are currently discussing with her the shape of a potential new senior role within MHP. We would like to thank her for her considerable contribution to the Company.
"Gay leaves in place a considerable team of senior practitioners with extensive financial services and particularly asset management expertise. We continue to expand and grow the MHP team, bringing in some of the best talent in the industry."
Collins began her career selling eurobonds to fund managers at Merrill Lynch and at Dean Witter in London and New York. Later she was involved in a MBO to set up Ludgate Communications, which was subsequently sold to Interpublic Group.
She is a member of Cancer Research UK’s 'Women of Influence' and was one of the mentors in PRWeek’s mentoring scheme that aims to tackle the lack of female leaders in communications.