Married. Joint non-registered account with mutual funds invested. Funds added over 10 years ago and records no longer available. Can 100% of T5 be claimed on spouses ?

Spouse is in 20% tax bracket and I am in 50% tax bracket. As the deposit to this account was done so long ago, we have no proof of who deposited this money. Last year we claimed 50% and 50%.  Can I  claim 100% on Spouse' return?