Former Lib Dem minister Sarah Teather has warned the rhetoric surrounding the debate over welfare payments will set "neighbour against neighbour", as she prepared to vote against her party.
On Tuesday evening MPs will vote on government's Benefits Up-rating Bill that would see benefit payments rise below inflation at 1% for three years.
The government argue the real terms cut is needed to save money as well as ensure benefits do not rise more than public sector pay, which has also been capped at 1%.
Speaking in the Commons, Teather, who lost her job as a children's minister in the September reshuffle, confirmed she would vote against the Bill and attacked the "strivers verses scroungers" framing of the argument.
"It will make society less generous, less sympathetic, less able to cooperate," she told MPs.
"The marginalisation of the underserving poor will place one group out of society entirely over time, and leave them less able to make choices about their own lives and less able to participate.
She added: "That fragmentation of society is, for me, the spectre of broken Britain, it is one we should worry about hastening at our peril."
Teather announced she would vote against the Bill during an interview with the BBC on Monday. "We have a huge problem with in-work child poverty and we're only going to make this significantly worse," she said on Monday.
She added: "I feel deeply anxious about the policy and I will be voting against the Bill tomorrow very reluctantly and with a very heavy heart."
Nick Clegg has defended his decision to support the Bill, arguing that without the Lib Dems the Tories would have taken an even greater axe to benefit payments - however many Lib Dem MPs and activists are uneasy with the move.