The Madonna Litta is named after a noble Milanese family who owned the painting for centuries. Although it is generally accepted that the work is by Leonardo, some aspects of the painting have led various experts to speculate that it could be a collaboration between Leonardo and one of his pupils or even a product of his workshop. Certainly, the landscape in the background is not the standard model so recognisable in Da Vinci's, Madonna of the rocks, Mona Lisa and St Jerome. However, Leonardo's stunning sketches of infants provide evidence of the master's hand in at least some parts of the work. The harsh outlines of the Madonna and Child are often cited as evidence that the painting is a product of the workshop rather than by the hand of Leonardo. However, the medium used was Tempera, which was perhaps not as suited to the subtle sfumato effects achieved by Leonardo when he was working in oils.
My own feeling is that the Madonna Litta was worked on by Leonardo's gifted pupil, Giovanni Antonio Boltraffio with the delicate finishing touches applied by the master himself.