He said he would stand up for all Londoners regardless of "colour or identity" as long as "you play part within the identity of this great city".
"People should remain as individuals and belong to the environment they come from or they come into.
"This is Britain, it is for the British people... it is not for people to enter into this land dictating what will or will not happen to the people that created it and built it over generations."
He was asked later on BBC London's Vanessa Feltz Show what he would say to people from ethnic minorities who might be afraid to approach him for help.
He said: "Do not be nervous. As long as you abide by our identity and laws of this land, come to me and I will see where we can help."
The BNP campaign focused heavily on tackling crime and stopping recent immigrants jumping ahead of people who had been on council housing waiting lists for a long time.
There were also pledges to scrap the congestion charge, pull out of the EU, plant more fruit trees and provide solar panels on public buildings.
But immigration is the BNP's best known policy area - they want an immediate halt to it, deportation of all illegal immigrants and they propose offering money for "voluntary resettlement whereby those immigrants who are legally here will be afforded the opportunity to return to their lands of ethnic origin".
We are particularly worried about the effect that the election of a BNP assembly member will have on race relations and community harmony
Dave Prentis Unison union
The BNP have had a number of councillors elected in recent years, but until these elections had never had anyone elected to a higher profile position.
The BNP campaign had prompted other politicians - and the Bishop of Barking among others - to call for voters not to elect the party.
Campaign group Hope Not Hate launched a huge operation across the capital to dissuade Londoners from voting for the BNP.
Gerry Gable from the group said: "A BNP victory means hatred, violence and stupidity.
"Richard Barnbrook being returned I think is a disaster for the BNP because the guy is inept, his track record had been dreadful. On his own he will sink without a trace."
Dave Prentis, general secretary of the Unison union, said: "We are particularly worried about the effect that the election of a BNP assembly member will have on race relations and community harmony."
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