Analysts cut the target price to 180p from 200p, arguing dividend cuts could put the status of real estate investment trust at risk.
According to the bank, like-for-like retail rent could decline by 10-13% if shopping centres around the country remain shuttered for at least a quarter.
In that scenario, landlords are estimated to bear around half of the rent loss or deferrals.
The recovery is expected to come in 2021 when deferred payments flow in.
Hammerson announced earlier on Monday that it is reviewing a flood of requests for waivers on a case-by-case basis.
Office space, in which Hammerson has small exposure, is “relatively immune to the crisis”, analysts said, though a prolonged health crisis “could potentially trigger higher rent losses in the office segment too”.
Shares slid 18% to 70.18p on Monday at noon.