The firm this week announced a deal by which it will pitch for business and jointly market services with the Belgian shop.
It follows a deal PI signed to work with Edinburgh's Pagoda PR earlier this year (PRWeek, 8 February) and marks another step in the company's attempt to establish a Europe-wide lobbying network.
Agency MD Andrew Dunlop and Houston founder John Houston said the arrangement would be exclusive but both firms would remain financially independent.
They have known each other since they advised Thatcher's Tory government - Dunlop to defence secretary George Younger and Houston to foreign secretary Geoffrey Howe.
Houston clients include JP Morgan Chase. PI clients include Virgin Atlantic and shipbuilder Vosper Thornycroft.
