Mr Livingstone wants to get rid of the pigeons because he believes they are a health hazard and create a mess in the area.

But campaigners had carried on feeding the birds even after the licensed feed sellers were banned two years ago.

Now a phased feeding programme has been agreed which the mayor hopes will reduce the number of pigeons.

I am confident that we have found a solution that will gradually reduce the numbers of pigeons in the square without causing them any harm Ken Livingstone, Mayor of London

The mayor blames the pigeons' corrosive droppings for causing �140,000 of damage to Nelson's Column and the square.

Since the feed sellers were banned, people have been employed to scare off the birds with hawks and megaphones and a vacuum device is used to suck up the seeds.

But volunteers continued to turn up every day to scatter seeds, attracting thousands of pigeons to London's most famous square.

Under the deal, an independent scientist will monitor the six-month feeding programme.

The feeding time will gradually be moved back from lunchtime to 0800 GMT and the amount of food slowly reduced.

Public arena

Campaigners have agreed to stop scattering seed and there will also be a ban on feeding the birds outside the official times.

"I am confident that we have found a solution that will gradually reduce the numbers of pigeons in the square without causing them any harm," Mr Livingstone said.

He wants to make the square a public arena for entertainers and introduce street cafes.

Work is already going on to pedestrianise the northern side linking it with the National Gallery.