I doubt they want better tax havens! They more likely want to regulate them more closely, or eliminate them.
The synonym is "tax shelter."
People who have money, and their lawyers, study the tax laws to find ways to avoid paying taxes. Many hide their assets offshore, or in Swiss banks. There are certain types of investments which are tax free, or which provide substantial "tax breaks."
Now that budgets are tight, we want to blame the rich and close the "tax loopholes."