Boris Johnson tells Cameron he must do more to win his support on EU

Mayor of London says PM’s pledge to ensure sovereignty of parliament needs more work if he is to back pro-EU campaignBoris Johnson has told David Cameron that he needs to do more to win his support for the campaign to keep Britain in the EU.The London mayor, who has kept Downing Street and the Conservative party guessing over which side he will support in the referendum, warned the prime minister that he needs to strengthen his plans to reassert the sovereignty of the UK parliament. Contin