I joined the organization 1.3 years ago as a manager without direct report at a Federally regulated organization. Throughout the year, the role has been impacted as not a lot of focus was on it. It was decided that eventually I would have a title change or transfer for another department. I received a positive performance review last year.

Yesterday, I was told that my role is no longer needed and they want me to switch to a role that is a lower grade than my existing role. The new role is 16% lower than my current salary. My employment letter has a Termination without Cause but no demotion clause. Is this considered a constructive dismissal or what legal grounds do I have? They say I have 2.5 days to accept the new role by Monday.