Dozens of staff face the choice between redundancy and moving to Manchester as a global insurance firm axes one of its London offices.
Ninety workers could lose their jobs when RSA closes its central Croydon base in July next year.
Just 15 of the 105 staff currently employed at the firm's Emerald House offices in Lansdowne Road will survive the chop.
Some of those whose jobs are at risk will be offered new positions in Manchester, where RSA moving the bulk of its Croydon business.
The company said it planned to retain scaled-back trading in Croydon and was looking into possible locations for a new, smaller site.
A spokesman for RSA said: "Following a comprehensive review we have taken the decision to vacate our current office in Croydon and move to a smaller market trading site.
"This will unfortunately put 90 roles at risk of redundancy but many will either be redeployed or take up vacancies in the new office.
"We are making every effort to support our staff affected by this."
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