Unite said the decision was a "bitter blow" to staff and customers as it accused the bank of "walking away" from local communities.
Lloyds said 29 Lloyds Bank and 15 Halifax branches would close, including the Lloyds branches at Queen Street in Morley and Town Street in Horsforth. It said customers were carrying out "significantly" fewer transactions at these locations.
Vim Maru, retail director for Lloyds Banking Group, said: "We've also seen our digital banking customers grow by over four million in five years, to almost 18 million, of which 13.6 million also choose to be active app users.
"This means that, like many businesses on the high street, we must change for a future where branches will be used in a different way, and visited less often.
"We'll continue to invest in our high street presence, as this week we're opening a new concept Bank of Scotland branch in Edinburgh, the only bank to take up residence in the new St James Quarter.
"Importantly, we'll continue to give our customers a choice in how they bank, with branches sitting alongside telephone banking, online and mobile banking, our video appointment services, our cashback through local shops programme, our participation in the industry BankHUB cash initiative and 11,500 post offices, at which our customers can bank and access cash."
Unite national officer Caren Evans said: "The decision by Lloyds to further erode its presence within our communities is baffling.
"The closure of 44 more bank branches will deny our communities essential services such as access to cash and experienced highly trained staff.
"A local ATM is not a suitable alternative to a staffed bank branch.
"In recent times Lloyds has spent significant resource to sell its message of 'Helping Britain Recover'. Unite seriously question how this decision to walk away from local communities promotes this message at a time when the customers will rely on the financial services sector support more than ever.
"Unite does not view the bank branch network as a disposable commodity and the union believes that the branch network has a value far beyond its immediate commerciality. Unite wants to see Lloyds Banking Group invest in the branch network and commit to a meaningful presence in our communities."
Lloyds said of the closures announced on Wednesday that more than a third are branches situated in or around cities and large towns with another branch "very close by".
It added that across the group's branches, transactions have fallen 10 per cent a year in the five years to March 2020, and significantly further in the year since.
Nine out of 10 customers have a branch within five miles of their home, it said.
Martin McTague, vice chairman of the Federation of Small Businesses, said: "Communities across England and Wales will be feeling a new wave of disappointment today, with the announcement of these closures coming fresh off a devastating delay to the June reopening.
"Bank branches are not only critical to those who still depend on cash - often society's most vulnerable - they also serve as a draw for shoppers, meaning footfall for surrounding small businesses."
The full list of branches closing
Lloyds branches :
Church Village (Pontypridd)
London Regent Street
London Berkeley Square
London Kentish Town
London Gants Hill
Oakham (East Midlands)
Brighton Preston Circus
Kempston (near Bedford)
Cheltenham Bath Road
Sedgley Dudley (Staffordshire)
Manchester Cross Street
Plaistow West Ham
Chesterfield Central Pavilion