According to CRA Attribution rules, what you need to do is determine who contributed to the investment and at what percentage. You report the interest or capital gains earned in the same proportion as the funds that were contributed into the account that earned the income. So only if these funds were contributed 100% by one spouse, would you claim the income on the T3, T5 or T5008 slips 100% in that person's name.
You cannot change the amounts strictly for tax advantages, and you should continue to report it with the same percentages each year, as changing this each year can trigger a review and possible reassessment from CRA. Generally spouse's claim 50/50.