Grey squirrels were spotted in 74 per cent of gardens at least monthly throughout the year, but red squirrels were seen at least monthly in just two per cent of gardens, and at least once a year in five per cent. In Scotland, that rises to 60 per cent of gardens.
Slow worms seen in just eight per cent of gardens throughout the year, and two per cent of households regularly seeing grass snakes.
Daniel Hayhow, RSPB conservation scientist, said: "Despite remaining widespread in many areas of the UK, important habitats for slow worms and grass snakes have been lost.
"As gardens become tidier, reptile homes have been lost, leaving a shortage of habitats in which to live and breed. Piles of logs, compost heaps and ponds provide ideal warm, sheltered environments for these species to breed, find food and to hibernate.
"By providing a shelter and a safe place to make a home, gardens provide an invaluable resource which are a key element in helping to save nature, perhaps even playing a pivotal role in reversing some declines."