He will lead a team that currently sits within MHP's M&A practice. The agency plans to separate these divisions, with Robb heading a financial services team numbering 10 staff initially.
Robb, who is to join MHP in December, has worked at Cicero since 2011, before which he worked in the in-house team at Betfair. He has also worked in the US, first on the Presidential Election in 2004 and then a US Senate race in Missouri in 2006 for incumbent Senator Claire McCaskill.
Robb will report to CEO Alex Bigg, who joined last autumn.
Robb’s appointment comes soon after that of Nick Barron, former head of corporate at Edelman, as MHP deputy CEO.
Bigg said: "We are delighted to welcome Mike at an exciting time for MHP as we continue to win new clients and build momentum across the business. His expertise and experience will be invaluable as we continue to grow our offering and cement our reputation as a leader in our industry."
Robb said: "MHP has an established track record of delivery and I look forward to supporting the ongoing transformation of the business and future vision, working with the team to ensure that story is told as widely as possible."
Recent client wins at MHP include uSwitch, Navigant, Harneys and Eastspring Investments.
Revenue at the Engine-owned agency grew three per cent in 2016 to £17.1m, according to PRWeek's UK Top 150 Consultancies table. It followed stagnant growth in 2015 and a dip in revenue in 2014.
Last week, Engine announced a restructure into four new business units to encourage closer collaboration. One of the units, called Engine PR & Activation and headed by Engine group MD Simon Peck, will include MHP and Mischief, as well as sports marketing agency Synergy and events consultancy Slice.