He replaces Kenny Bain who has decided that now is the right time to step down from his role.
Robertson has over 30 years' experience in the dairy industry and has held senior executive positions with Arla Foods, Milk Link and Glanbia. Latterly he was Vice President for Arla Foods, responsible for 12 cheddar and mozzarella manufacturing and packing sites across the UK & Denmark.
First Milk chief executive Shelagh Hancock commented:
"Much has been achieved over the past two years during our 'turnaround phase' to put the foundations in place for our future growth and development. Nevertheless, there is more that we can do to drive business performance by improving the efficiency and productivity of our operations, and achieving this will enable us to deliver a better return to our Members.
''I am delighted to have been able to bring on board someone of Mark Robertson's calibre and proven track record to lead this process at our manufacturing sites. He not only has a wealth of experience and knowledge of cheese & whey manufacturing, but also has considerable leadership qualities and a 'will to win' mentality that he has used to consistently deliver results.
"Kenny Bain made a significant contribution to the turnaround of the business over the past two years to improve quality, reduce costs and successfully deliver significant capital investments to improve site capabilities. He departs at the end of the month with our best wishes."
On his appointment Robertson added: "I am excited about the opportunity to lead the Operations team at this time and by working together I know there is a real opportunity for us to deliver for the business and for our farmer members."