If you are claiming the
spousal amount in the year that you separated, you would only use the
income that your ex earned while you were together. So...if you
separated February 1st, then your spouse's income in January is used
to calculate the credit.
http://www.cra-arc.gc.ca/tx/ndvdls/tpcs/ncm-tx/rtrn/cmpltng/ddctns/lns300-350/303/menu-eng.html