It says the withdrawal of the Christmas bonus from pensioners and other social welfare recipients will put families who are already struggling under extreme pressure.
Launching its annual appeal, the country's largest charity said that demands for help were up by 30% in some areas already.
It also said that one in four calls were from people new to the society.
Charity shops can be a good barometer of the impact of the recession.
St Vincent de Paul's 100 shops around the country are 10% busier this year than last, but spending per customer is down.
This year, in the Dublin Archdiocese alone, new shops have been established in Lucan and in Malahide and two more are scheduled to open soon in Greystones and Kilcullen.
