Instead, bird tables should be stocked with a healthy mix of seeds or worms, grated cheese, porridge oats or soft apples, bananas or strawberries.

Birds are also partial to biscuit crumbs, leftover jacket potatoes, cooked rice, breakfast cereals and pastry.

"Bread is often thrown out to the birds but it doesn't actually contain any of the vital ingredients to provide birds with the energy they need to breed and feed," said Val Osborne, the RSPB's head of wildlife inquiries. "We are asking people to consider alternatives."

Birds' diets are particularly important at this time of year when they are trying to feed chicks.

Their young need food that is high in nutrients if they are to stand a good chance of reaching adulthood. Peanuts and pieces of fat can also harm nestlings.

The RSPB says that garden birds may need extra food throughout the year.

A spokesman said: "The RSPB believes that whilst not harmful, it doesn't actually provide birds with any goodness or nutrients.

"It could even prove detrimental, as the birds will fill up on it and not other, more nutritious foods."

In a survey earlier this year, the charity said the average number of birds spotted in each garden has fallen by a fifth since 2004.

Milder winters, fewer hedgerows, the use of pesticides and wooden decking in gardens are all thought to have fuelled the long-term decline of some species