Mr Wilson stopped lobby briefings

But others attribute its success to mutual trust between spokesmen and the Press.

However, not everyone has seen it this way.

Labour's longest serving prime minister, Harold Wilson, at one point drew a halt to the briefings, claiming the lobby could not be trusted.

Sources

It was suggested that its members had spotted a deliberate attempt to mislead them.

The Guardian, The Independent and The Scotsman boycotted the lobby meetings in the late 1980s, protesting against only being allowed to quote "Downing Street sources".

The lobby is named after the Members' Lobby at Westminster, which journalists have a right to enter - except during a division - in order to interview MPs.

Information passed to journalists in these circumstances is often given on the understanding that the source will not be revealed.