This is a great question. It would be helpful first to note that Structural adjustments policies refer to the work and intervention of the International Monetary Fund (IMF) and the World Bank. In addition, these Structural adjustments are usually aimed at poorer countries that seek either to obtain new loans or reduce the interests rates on existing loans.
At this point all seems well. However, when these countries approach the IMF or World Bank, there are certain conditions that will have to be followed or met, if new conditions are in place. From the point of view of the IMF and World Bank, these conditions are to help the country, but critics see this as tantamount to blackmail. This is why there is controversy.
Usually the IMF and World Bank would like these countries to expand their manufacturing by seeking to privatise industries and deregulate things on a political level. A free market mentality is introduced, as one can see. Also critics will point out that the ones that stand to gain most are the wealthier nations that do not need help.
If these countries do not follow suit, there can be punitive actions, usually in the area of finances. Being that these countries are already poor, they have little leverage. In light of all this, critics want the IMF and World Bank to help with little or no conditions.