Burren Energy tumbled 10pc yesterday as a number of founding investors sold 24.5m shares, representing 17.9pc of the oil and gas exploration group.

The companies had invested in Burren when it floated at 130p last December. Traders said Capital Group, AIG and ING were among the investors reducing their holdings although chief executive and founder Finian O'Sullivan is understood to have held on to his 4.4pc stake.

Seymour Pierce placed the shares at 325p. Burren Energy fell 36 to 325p.