Home Secretary Theresa May has been urged to ban racist, anti-Semitic and homophobic extremists from gathering in central London in an event planned to take place the day before Monday’s Holocaust Memorial Day.

Gabor Vona, the leader of the Hungarian nationalist party Jobbik, is planning to meet members of Golden Dawn – some of whom have openly expressed admiration for Adolf Hitler – and the British National Party (BNP) in Holborn on Sunday.

London Assembly Member Andrew Dismore, who as a Labour MP founded Holocaust Memorial Day and chaired Parliament’s Joint Committee on Human Rights, told the Jewish News that Jobbik is “the most powerful outwardly fascist political party in Europe”.

In his letter to the Home Secretary he said: “I have no doubt that all decent thinking people in London will join with me in demanding that the Home Secretary says ‘No to Jobbik’ “.

“While I advocate the right to free speech in our society, this must also be balanced against other human rights.

“It is particularly important to note that his event is being held on the eve of Holocaust Memorial Day when the offence of his meeting will be all the more damaging.”

Last week, a memorial honouring gay victims of the Holocaust was unveiled in Tel Aviv.

It features a concrete pink triangle, the same symbol used by the Nazis to mark someone as gay.

According to the US Holocaust Memorial Museum, over a million German men were targeted by the Nazis for threatening the “disciplined masculinity” of Germany, and over 100,000 were arrested under a law criminalising homosexuality.

Approximately 50,000 served prison sentences as “convicted homosexuals”, and around 5,000 and 15,000 gay men were imprisoned in concentration camps.

Golden Dawn has been on the ascendancy in Greece ever since the country’s 2012 economic crash and its supporters have been linked to a significant number of attacks on migrant workers, rival political groups and LGBT citizens.

In October 2012, a Golden Dawn MP was captured shouting homophobic and racist insults at a theatre director in Athens

The party forced the director into closing a production of Corpus Christi, which portrays Jesus Christ as a gay man.

BNP leader Nick Griffin, known for his racist and homophobic behaviour, was declared officially bankrupt earlier this month.

He supports the efforts of Golden Dawn in Greece.

The 54-year-old previously described gay people as “creepy” and admitted that he would like to ban civil partnerships.

In October 2012 he was criticised for posting the address of a gay couple on the internet and calling for his supporters to demonstrate outside their Cambridgeshire home.

It was over the decision of Reading County Court to rule in favour of Michael Black and John Morgan; the pair were prevented from sharing a room together at the Swiss Bed and Breakfast in Cookham, Berkshire, in March 2010.