A charity for the homeless has claimed some people in Cornwall will struggle to keep a roof over their heads when housing benefit is cut.
Reforms including a £400-a-week cap for the largest homes are due to start in April under changes being debated by MPs on Tuesday.
Shelter in Cornwall has predicted an increase in evictions.
Ministers have said the housing benefit bill got out of control under Labour and needs to be cut back.
Ian Byworth from Shelter said: "The reality is that we are going to be facing much more homelessness and more evictions because of this.
"Cornwall's low incomes mean that lots of hard working people do have to claim housing benefit.
"There has to be change, but in a considered way that does not affect the vulnerable and poorest in our society."
Liberal Democrat MP for St Ives, Andrew George, said: "It will put a lot of families in extreme stress and ministers should think again.
"The impact on Cornwall is likely to be very severe indeed."
The National Housing Federation says 8,450 households in Cornwall will be affected.
Prime Minister David Cameron has insisted the government will be pressing ahead with the cap plan, saying people would still be able to claim up to £21,000 in annual benefits.