2 Answers

It could be a blocked drain or a kink in the drain hose, check those, if it's not that then it's time to see a repair guy.

You do not mention the brand washer. 

It could be the belt is wearing out 

or

This is for maytag: 

Instructions
1
Do not use any detergent other than HE (High Efficiency) detergent if your Maytag washing machine calls specifically for HE detergent. Too much suds in the washer can slow the speed at which the washer is able to spin and dry clothing and result in clothing not being able to get dry.

2
Move the drain hose to a lower location if it is at a height of greater than 96 inches. A drain hose that is this high makes it difficult for the water to flow from it because the water must fight gravity to climb such a significant height to leave the hose.

3
Move the washing machine away from the wall and make sure that the drain hose is not stuck between the appliance and the wall or the appliance and the floor. A drain hose that is pinched or that has a kink in it is not able to allow water to freely flow through it.

4
Place more clothing in the washer if there are only a couple of small items in the washer. Not including enough clothing in the washer causes an imbalance that restricts how well the washer is able to eliminate water during the spin cycle.

5
Do not pack the washing machine so tightly with clothing that there is not room for the clothing to move around a bit as it is being washed.

6
Set your Maytag washer to wash on higher spin speeds. The faster the spin cycle is, the more effective it is at removing water from clothes.

Read more: My Maytag Washing Machine Won't Spin All the Water Out of the Clothes | eHow.com http://www.ehow.com/how_7714111_maytag-spin-water-out-clothes.html#ixzz2EZVBWVCp