She will join the agency's public affairs practice later this month as associate director.
Richardson's appointment comes less than a month after Edelman snared Tory campaign director for the London region Peter Bellini (PRWeek, 13 November).
A former commissioning editor on the Standard, more recently Richardson has written on education and the public sector for the paper.
She has also spent five years as a cabinet member at Westminster City Council, and in 2005 stood as the Conservative parliamentary candidate in Leicester West.
Richardson is said to be well connected in Conservative circles and is married to Damian Collins, the highly regarded Tory prospective parliamentary candidate for the safe seat of Folkestone & Hythe. Collins is a consultant at Lexington Communications, but is seen by many in the party as future ministerial material.
At Edelman, Richardson will report to the agency's managing director for public affairs Alex Bigg. Meanwhile, Bellini began his role this week as senior consultant in Edelman's public affairs practice after five years working for the Tories.
Bellini started out as an agent for the Selby region, but spent the past three years as a campaign director for the London region, working out of Conservative Central Office.