Washing machine filling with water when not in use?

Had a brand new washing machine (whirlpool) put in and it gradually starts filling up with cloudy water over a period of a couple of days. It was put in in a great hurry by a neighbour. He attached it to the hot water supply and another neighbour said that was wrong and switched it to the cold water supply. No difference. The sink also gurgles really loudly when the washer is in use. Do I need to get a plumber out to install it properly or can I fix the problem myself?