The number of abandoned cats reported to the organisation in 2010 rose to 10,610, a 28 per cent increase on the previous year, which itself saw a 40 per cent rise on 2008.
Many of the charity’s shelters are so full that RSPCA officers have been finding private boarding or foster homes for the animals.
Dog charities also disclosed that they faced an increase in the number of animals they were forced to put down.
Figures showed a total of 7,866 dogs were taken to Battersea Dogs And Cats Home in south London in 2009, of which 2,815, or 36 per cent, were destroyed.
Some 69 per cent of those destroyed were healthy but judged too much of a risk to be offered for re-homing because of their temperament or behavior.