My senior colleague is torturing me

I work in a IT firm in Bangalore. I am in deputation with a reputated firm in bangalore. I am working in a project where I am working independently. I am a technical writer. I was asked to do R&D on a Freeware tool. I analyzed it and put all my efforts. But later, after few weeks my senior colleague, who was guiding me started torturing me. Every now and then he use to ping me in commutator and asks how much did you do and gives taunt and demotivated me. Till now my work has not been started. I am doing R&D with the tool, which is not my part of work. But still yes I am doing it because I found that it will be a great learning. It's been a month now and still doing all the work but I am stuck on between so took help from R&D team. They helped me but again few pary of work has been shifted to me as requested by my senior colleague. I am facing lot of pressure and demotivations from this person. Next week I am going on leave and this person in front of another person says that why haven't you done this, what are you waiting for, waiting for your vacations. He taunts me everyday. As this R&D is not my work still I am.trying my best. I have escalated about my work to my parent company's manager but not one are taking any actions. I am facing lot of issues with this person. Please suggest me what can be done. Should I escalate his behavior to my manager. I have no hope from my manager. Please suggest.