Billboards, paid for by Unison, have been put up across the city suggesting that nurseries and care homes are under threat.
The same posters have also appeared in other major cities, including London, which are Labour targets. They urge voters to choose the “party that cares”.
But Southampton’s Tory Cabinet member for children’s services Jeremy Moulton hit back at the claims made on the billboards, saying the city’s nursery provision was not under threat and there were no plans to close care homes.
“The unions should be ashamed of themselves for these despicable tactics. They are needlessly worrying local families for their own political ends,” he said.
He said Conservatives were pledging to create an extra 1,800 nursery places for two-year olds by 2014 and have pledged to protect all 14 city Sure Start Centres.
Meanwhile members of the Unite union have been door knocking and delivering leaflets in Labour target wards around Southampton urging residents not to vote Conservative. They have also written to all council staff asking them to vote Labour.
Both unions have also set up a phone bank campaign to work through lists of city voters.
Tory leader Cllr Royston Smith said: “Labour constantly talks about party funding but here they are in Southampton benefiting either directly as individually funded candidates or indirectly as the beneficiary of the unions high-profile attack on the Conservatives. It’s somewhat hypocritical.
In my opinion, the unions are trying to buy Labour an election victory on Thursday.”
Cllr Smith, who recently threatened to withdraw taxpayer funding for union officials at the council, accused the unions of using their leaflets to scare voters into voting Labour.
A Unite union newspaper, dubbed the “Royston Record” also personally attacks Cllr Smith.
Mike Tucker, the city’s branch secretary for Unison, said the posters were part of a nationally funded billboard and advertising campaign and were being used in Southampton among other cities as it was seen as a “crucial election”.
He denied the posters were misleading saying the Conservatives had already closed two care homes and the future of the other homes was under review.
He added although Conservatives had not physically closed buildings he said staff levels in SureStart children’s centres were being run down.