The Rocks centre-half, who can also play in midfield, has been one of Bognor’s most consistent performers over the past couple of seasons and losing him is a big blow.
He is the first of the 2015-16 squad to leave Nyewood Lane and Rocks fans will be hoping it does not signal the start of a series of departures.
The Daggers have just been relegated from League Two into the top tier of the non-league game and it is believed Robson will be full-time with them.
Rocks general manager Jack Pearce said: “We wish Craig all the best and thank him for his service to the club.”
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