BT has failed to invest enough money into its nationwide full-fibre broadband network, that’s according to the boss of a rival internet supplier. Rajiv Datta, chief executive of full-fibre brand Nezfibre, has accused BT of behaving like a “typical monopoly”. Mr Datta told The Daily Telegraph that BT had dragged its feet and only started to seriously invest in the next generation of internet when faced with competition from his firm and others. “When you have somebody that has the dominant market share and has had the benefits of being the incumbent all these years, not investing in that core i…