Her appointment is part of the company's plans to unlock investor access to high-quality corporate debt and sovereign insurance, it said.
Parsons has over 25 years' industry experience, having most recently served as head of fixed income strategy at Winterflood Securities, prior to which she worked as a retail gilt-edged market maker.
She also serves as founder and chair of the Investor Access to Regulated Bonds (IARB) working group, and is a member of the London Stock Exchange Group's primary markets group.
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Alongside Tom Capon, chair of City Future, Parsons launched the IARB working group in July 2022, with the aim to secure improved investor and discretionary wealth manager access to regulated transferable bonds, with lower denominated issuances.
Parsons said debt capital markets remain "largely inaccessible" to UK retail investors and wealth intermediaries in the UK. However, she argued that "imminent changes" in regulation will bring the UK in line with other regions with an "extraordinary take up" of direct ownership of sovereign and corporate debt.
"These reforms will allow issuers to engage retail capital and offer new listed investment opportunities for investors," she said.
"PrimaryBid has demonstrated how an innovative platform can deliver fundamental industry change by combining smart client solutions through technology and deep industry partnerships."
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Anand Sambasivan, CEO of PrimaryBid, added: "[Stacey] brings in-depth sector knowledge, an unrivalled track-record, and superb leadership credentials. At PrimaryBid we are committed to delivering more inclusive capital markets that work for everyone. Stacey's appointment will be pivotal in helping us achieve this goal.
"Our infrastructure has turned the historical challenges of including individuals and communities into opportunities, leveraging new technology and partnerships to make investor inclusion not just feasible but seamless and strategic."