"Big Brother-style" lie-detectors will be used by Cornwall Council leaders to trap benefit cheats, according to a cabinet member who last night resigned.
Fiona Ferguson, portfolio holder for corporate resources, said she would not be part of the "subterfuge" to try to catch those who try to fiddle the system because the software was "not proven".
Capita were the contractors drafted-in by the council to install so-called "voice risk analysis techniques" on the telephone system to discover if those claiming the single person's council tax discount are genuine.
Mrs Ferguson said fellow Tory and council leader, Jim Currie had accepted her resignation after the pair had "agreed to differ" over the issue.
Mrs Ferguson said: "I think this smacks of Big Brother and I don't believe it's right.
"I won't be a part of the subterfuge which is why I've resigned now.
"I don't think the council were going to make a big splash of telling people.
"I'm worried this will put genuine people off from speaking to the council."
Mrs Ferguson, who entered the cabinet just three months ago, remains leader of the Conservative group on the council and will carry on as a councillor.
Mr Currie said: "There is tremendous pressure on the council's budget and we need to do everything we can to prevent fraud. This will not affect people making genuine claims."
In recent months, Mrs Ferguson has been at loggerheads with fellow Conservatives and other council members over the budget she helped draw-up.
Mrs Ferguson argued for a 0% increase in council tax while others called for a rise of 1.97% to combat government funding cuts – she rejected claims quitting cabinet was to dodge the wrangle.
Alex Folkes, Lib-Dem leader on the council, said: "With recent events I think she was looking for an excuse to leave the cabinet."