The other two divisions are: advertising/PR, headed by Philip Gregory; and design, the chairman for which will be announced shortly.
The marketing division includes: digital agency Twentysix London; direct agency Clark McKay & Walpole; and Wax, the result of the merger in September of three Media Square companies, Catalyst, Dynamo and Theatre, specialists in sales promotion and experiential marketing.
Spicer was until recently managing director of Arc Worldwide, where he has spent the majority of his career and where he became managing director in 2004.
Spicer said: "My challenge is to develop the reputation of the marketing division and each brand within it to represent best practice, innovation and the best in class."
The hiring is part of a programme of change initiated by Parry, who was parachuted in by agitated Media Square shareholders to sort out the company in July after a £3.2m annual loss.
Parry spoke to Brand Republic about his plans ahead of a fuller presentation to investors tomorrow [Tuesday], when the company will reveal its interim results for the six months to August 31.
His view is that Media Square got itself into a mess after making the "ultimate acquisition too many", the £63m purchase of 16 marketing services businesses from Huntsworth in late 2005.
Parry, chairman of publishers Future and Johnston Press and was a director of ad agency group WCRS, said his remedy for Media Square was sell off some minor parts and reorganise the rest into a more focused business.
The previous management's mistakes were to leave the "huge mass" of agencies they had acquired as separate, standalone business units, in the hope someone would buy them one by one, according to Parry.
His and development director Peter Reid's programme is reducing the collection of more than 30 individual business units to 12, within three divisions.
Parry said: "What we're going to do with it is focus the whole business on three professional disciplines: advertising and PR; marketing; and design."
The three divisional chairmen will be beneficial to the holding company's relationship with individual agencies, according to Parry, who was critical of the previous management's relationship.
He said: "When people businesses are not nurtured and managed and invested in and run, they very quickly decline.
"So if you take the example of CMW -- the C, the M, and the W [Clark, McKay and Walpole] left because they weren't persuaded to stay or they couldn't get a deal. And the next generation of management couldn't persuade their owner, the holding company, to invest in the business by putting in creative people and account handling people."
Parry said Media Square was likely to steer clear of further acquisitions for six or eight months but he would then be interested in buying a London-based PR agency.
The companies the group has already sold off since Parry's arrival include sports sponsorship agency Redmandarin.