Investing.com - The euro fell more than 1% against the dollar on Monday and weakened against the yen amid fears that a possible British exit from the European Union could have a negative impact on the euro zone. EUR/USD hit lows of 1.1004, the weakest since February 3 and was last at 1.1015, off 1.07% for the day. The single currency fell to three-year lows against the yen, with EUR/JPY down 0.64% at 124.56, the lowest level since April 2013. The euro strengthened against the broadly weaker pound, with EUR/GBP advancing 1.22% to 0.7821. Fears over Brexit mounted after London Mayor Boris Johnson said Saturday that he would back the campaign for Britain to leave the EU in a June 23 referendum. The announcement dealt a blow to U.K. Prime Minister David Cameron’s campaign to remain in a reformed EU after he reached an agreement with the bloc’s leaders late last week. Earlier Monday a handful of senior Conservative party members said they would also campaign for a British exit and some of t...