The parent firm that was responsible for supervising construction was Samuel White of Cowes, Isle of Wight.

This was a then-new role, and the class was configured for working in the shallow water of rivers, estuaries and shipping channels.

The engines of this class were Paxman diesels, some of which were built under licence by Ruston and Hornsby of Lincoln.

Each vessel had: two 12YHAXM (intercooled) for main propulsion, rated at 550 bhp (410 kW) at 1,000 rpm, plus one 12YHAZ for pulse generation.

The class shared the same basic hull as the Ley-class minehunter and the Echo-class inshore survey craft.