An adviser to mayor Ken Livingstone has resigned after lying about taking a free luxury weekend in Africa.
Rosemary Emodi went to Nigeria in November
Rosemary Emodi, deputy to the mayor's chief race adviser Lee Jasper, last week denied visiting a £200-a-night resort in Nigeria last November.
But when the BBC confronted her on Tuesday with evidence she flew there with airline Virgin Nigeria, Ms Emodi immediately tendered her resignation.
The mayor's office said a formal statement made by Ms Emodi was untrue.
Virgin Nigeria confirmed Ms Emodi flew from London to Lagos on 30 November, stayed for three nights and returned on 3 December.
She stayed at the La Campagne Tropicana resort in a £200-a-night chalet paid for by her hosts.
With her was Eroll Walters, the director of community group Brixton Base Limited, head of the Black Londoners Forum and a friend of the mayor's advisor Lee Jasper.
Nigerian websites reported that London representatives were there to finalise a link with Kamp Afrika which runs educational retreats for young people.
But the mayor's office said it had given no approval or backing for any official link-up with Kamp Afrika.
As a senior employee Ms Emodi would be required to clear any official business in advance, or with private trips declare on the register of interest that she had received free flights and accommodation.
Ms Emodi was formally questioned about the trip by the Greater London Authority (GLA) when the BBC made enquiries last week.
In a statement released on 15 January the GLA said: "Rosemary Emodi has never visited La Campagne Tropicana and neither has any other representative of the GLA".
But when the BBC presented the latest evidence of her trip, the mayor's office said her statement was untrue and she had resigned.
A spokesperson said: "It has now become clear that the formal statement made by Rosemary Emodi was untrue. She has resigned with immediate effect."
The GLA said there was "no suggestion GLA funds were used for the trip" but all staff were required to honestly answer questions put to them.