Britoil PLC has rejected an increased takeover offer from British Petroleum Co. that values Britoil at about $4.45 billion. “BP has consistently failed to recognize Britoil’s true worth. Its latest offer still significantly undervalues Britoil,” Britoil Chief Executive David Walker said as he rejected the sweetened offer from the oil giant. The British government has said it would block any bidder from obtaining control of the board of Britoil, an independent North Sea oil company based in Glasgow, Scotland. Britoil already has reached a competing, friendly agreement with Atlantic Richfield Co. to acquire a partial stake in Britoil.