Nick Griffin is the leader of the far-right party
A British National Party (BNP) London Assembly member who invited his party leader to a Buckingham Palace event has been asked to "revisit" his selection.
The Greater London Authority (GLA) wrote to Richard Barnbrook after he chose Nick Griffin as his guest for the garden party hosted by the Queen.
Mr Barnbrook has been warned that his nomination will be reviewed if he does not change his choice of guest.
The BNP said Mr Barnbrook would comment on the matter on Tuesday.
Like all the other members of the London Assembly, Mr Barnbrook is in line for two tickets to the party on 21 July.
But in the letter, GLA deputy chief executive Jeff Jacobs warned the far-right politician to change his controversial guest or face having his nomination for the event "reviewed".
He also asked Mr Barnbrook to stop exploiting the situation for "publicity".
Mr Jacobs wrote: "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."
London mayor Boris Johnson has accused Mr Barnbrook of turning the Buckingham Palace garden party into a "political stunt".
A BNP spokesman 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?"
The party campaigns for the "voluntary resettlement" of non-white British citizens back to their countries of origin.
It also lobbies for the preferential treatment for British workers in the job market.
Buckingham Palace has said the London Assembly is one of more than 1,000 organisations given allocations of places for individuals at the garden parties.