Job centre access

I am expected to attend my JobCentre this week to hand in a Duplicate MR request ( they have lost the original )
My JobCentre is next door to the assessment centre, with parking for staff only for both buildings using the same barrier entrance.

When attending my assessment the barrier was lift to allow me to be dropped off near the entrance ( avoiding steps & a very long looped ramp ) & picked up after. ( I am a blue badge holder )
This visit to the next door building the job centre advisor point blank refuse to open the barrier to enable me to be dropped off, stating health & safety & other guises.

Are they legally obliged to enable me access?

( I am Not in a wheelchair but, I am on crutches as I cannot weight bear on my right leg at all - I find steps daunting with or without crutches & could not manage the “ramp” which I’d estimate to be about 250metres looping then the additional walk to the actual centre )