"After careful review we have identified around 600 roles where off-shoring will achieve significant cost savings. The number of full time employees impacted by this decision will be significantly less, as we expect at least a third of the role reductions to be met by closure of vacancies, temporary contracts, and natural turnover," the London-headquartered firm said in a statement.
"Maintaining good customer service while achieving cost efficiencies remains central to our organisation. We appreciate this is a difficult time for our staff and will be working closely with those affected to ensure they get all the support they need," it added.
Unite, one of the country's leading workers' unions, claimed those jobs were being switched to Pune.
"Aviva is betraying its UK workforce by exporting 600 jobs overseas. This is an appalling way to treat the loyal workforce who are the backbone of the company," Unite national officer Dominic Cook said.
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"Unite is calling on Aviva to reverse this decision and to keep the jobs in the UK. Aviva has a responsibility to the communities it profits from. It's bad enough exporting jobs overseas when the UK economy is strong, but when Britain's economy is suffering it's outrageous that the insurer isn't supporting employment in the UK," he added.
It has now said the final total is likely to be much less, possibly around 400.
The changes would largely affect administrative posts in its life insurance operation, which are mostly based in York.
Staff were briefed yesterday about the switch, which will be completed by next year.
Aviva, which employs about 31,000 people worldwide, is trying to reduce costs by more than 400 million pounds.