The British National Party leader Nick Griffin was today facing being effectively barred from attending a Buckingham Palace garden party.
The right wing politician had been invited to the social event by BNP colleague Richard Barnbrook who, as a London Assembly member, was nominated for two tickets by the Greater London Authority (GLA).
But Jeff Jacobs, the GLA's deputy chief executive, last night wrote to Mr Barnbrook telling him to change his controversial guest and stop exploiting the situation for "publicity", or his nomination would be "reviewed".
In recent days London Mayor Boris Johnson and Darren Johnson, chairman of the London Assembly, have both spoken of their concern about Mr Barnbrook's chosen guest.
In his letter Mr Jacobs said: "While elected representatives may and do attend, the event is a social occasion hosted by Her Majesty and it is inappropriate to exploit this privilege for party political purposes."
He added: "However, in the light of the views expressed by the Mayor and chair of the assembly, reinforced at yesterday's assembly meeting, I am writing to say that the authority may need to review its position in relation to your nomination unless you revisit the selection of your guest with a view to avoiding further controversy and desist from any further publicity."
If Mr Barnbrook does back down and take another guest there is still the prospect the Queen could find herself meeting the Far Right politician.
Any potential greeting might resemble the moment when the Prince of Wales shook hands with Zimbabwean president Robert Mugabe after he was "caught by surprise" at the funeral of Pope John Paul II in 2005.
The BNP campaigns for the "voluntary resettlement" of immigrants back to their countries of origin, claims white Britons have become "second class citizens" and wants to bring back corporal and capital punishment for criminals.
A BNP spokesman said Mr Barnbrook would not comment straight away but would make a statement on Tuesday about his decision.
The organisation said on Thursday: "You can't withdraw the invitation because you don't agree with someone's views.
"How is it going to look if the three main political parties conspire to deny us our rights - and the people that voted for Richard.
"They are seeking to subvert the democratic process."
The London Mayor was concerned about any potential embarrassment to the Queen if Mr Griffin had been allowed to join thousands of guests on the Palace lawns on July 21.
Speaking during Mayor's question time at City Hall on Thursday he said: "I do think it is essential that the Assembly sort this out and make a proper representation to whichever body is necessary to insure that the Queen's garden party, which is a happy annual event at which the service to the community of thousands of people is recognised, is not turned into a political stunt."
The garden party will come after the June local and Euro elections, which could see the BNP gaining more local council seats and their first MEPs.
Disillusionment with mainstream politicians over the MPs' expenses scandal and fears over jobs and immigration could lead to a surge in support for the party, according to political experts.
Buckingham Palace have said the London Assembly was one of more than 1,000 organisations given allocations of places for individuals at the garden parties, and the organisations themselves then nominate people to attend.
The nominations are then sent to the Palace for consideration before the invites are issued.
The anti-fascist group Searchlight said: "Common sense has prevailed. Nick Griffin is a criminal and a racist, he has no place at Buckingham Palace."Reuse content