HELP!! Leaking from under sink when i turn the washing machine taps on?

Ive got a new washer as old one broke, ive connector both the blue/cold and red/hot pipes under the sink but when i turn the water on (that black switch thingy) on each pipe i start to get quite a big leak (drip,drip drip drip) it would defo fill a big washing up bowl within an hour or two. The leak is coming from just under the blue pipe even when i turn that tap off and the hot tap on ...the leak still appears to come from the same spot?? help please !!