The cuts, which had been rumoured, were "still a shock", NUJ negotiator Jenny Lennox told Journalism.co.uk.
Jobs will go in Twickenham and Sutton as they lose their entire sports and leisure department of eight people consisting of two editors, two sport writers, two leisure writers and two subs, the union explained.
The changes would mean news, sport and leisure for seven newspapers would be produced by a total of only 12 reporters and two editors, the NUJ said in a statement.
Earlier this month journalists at Newsquest South London voted unanimously to ballot for strike action following claims further redundancies are being carried out at titles in the area. The ballot result is due on Tuesday, 31 May.
Staff at newspapers in Surrey, Sutton and Twickenham have been working to rule since 15 April.
At the beginning of this month members of the NUJ in the region made a unanimous vote of no confidence in London managing director Roger Mills and south London advertising director Dene Stuart, following an announcement of further editorial redundancies.
Lennox said the affected staff are angry. "The journalists had given suggestions as to how the company could make more money but the cuts were announced before the suggestions had even been considered," she told Journalism.co.uk
In a statement she said: "These cuts threaten the future survival of local newspapers in south London. Newsquest makes millions of pounds worth of profit and at the same time they want to axe our members jobs and retreat from quality local journalism.
"The union is balloting for action in response to the cuts because we know our members take pride in their work and local citizens wants to read a local paper which contains local news, sports and leisure."
No one from Newsquest London was available for comment this lunchtime.
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