You can't remove it without her consent, you need a solicitor. Your wife is entitled to some of what's been paid on the house if you want to keep it and if you can't afford to pay her off you may have to sell up. If your ex wife insists on staying on the mortgage she has to be contributing towards it.
BTW: You do not have to contribute to the mortgage if you no longer live there....regardless of who is on the mortgage, deed,etc....once out of the house, you are free to keep your money and stick it to the person who lives there....but you are STILL entitled to proceeds should you decide to sell the house....I should know, because my ex did this to me.
I am not sure what a mortgage deed is, but I can't think that anyone would object to being removed from the mortgage responsibility. In the US we have a thing called a quick-claim deed. You could make the argument that if she deeds the property to you, you will have it refinanced thereby relieving her of any mortgage responsibility.