The Accord union reprents form HBOS employees now working at Lloyds
A union claims Lloyds Banking Group is proposing 160 job losses in Cardiff as part of 5,000 across the UK by the end of next year.
The union, Accord, said most of the losses were likely to come from the closure of an office in Newport Road.
General secretary Ged Nichols said it was a "halfway house" announcement that would not end uncertainty for staff.
Lloyds has said most of the losses would be in its IT, collections and payment services.
The bank said that as some of these cuts refer to temporary staff, the end result would be a permanent loss of 2,600 jobs in the UK.
Accord, the union that represents the largest number of former HBOS employees now working in Lloyds, said the losses in Wales would centre on the Cardiff office.
This processes mortgages for the group's Birmingham Midshires brand, which is due to close in December 2010.
Mr Nichols said: "We've got plenty of time to look for alternative roles [for them] in the Lloyds Banking Group which is still a significant employer in south Wales for those people."
He questioned why it was necessary to say those jobs were going.
He added: "I'm in favour of being transparent and giving people notice, but today we only heard from two of the bank's divisions.
"We haven't yet heard from the retail division, which is the biggest one. We haven't from the wholesale division. So why release figures for the whole of 2010 for only part of the business? It's got to be all one thing or all another.
"If you are gong to make major announcements about the whole of 2010 which is supposed to clarify matters and settle the workforce down, so that those that are not affected know that, and those that are affected can make plans, then you've got to do the whole thing. Today we've got a half way house."
Last week, Lloyds, which is 43% owned by the taxpayer, said it would receive another £5.7bn in taxpayer support from the Treasury and sell at least 600 branches.
Fellow bailed-out bank Royal Bank of Scotland also announced last week that it would cut almost 4,000 retail banking jobs across the UK.