Labour is "absolutely resolute" on tackling "abhorrent" anti-Semitism, leader Jeremy Corbyn insisted as the party was hit by a fresh allegation about one if its councillors.
The Labour leader said there is "no place for any racism of any sort" within the party and said swift action is taken in any cases which come to light.
He was speaking after councillor Aysegul Gurbuz was suspended by the party over messages posted on her Twitter account claiming that Hitler was the "greatest man in history" and suggesting that Iran could develop a nuclear weapon to "wipe Israel off the map".
Mr Corbyn told BBC One's Andrew Marr Show: "Anti-Semitism is absolutely abhorrent and wrong. Anyone that commits any act of anti-Semitism, that makes anti-Semitic remarks, is auto excluded from the party and an inquiry follows immediately.
"We have suspended, we will suspend, any member that behaves in that way."
The allegations over Ms Gurbuz follow a series of incidents involving anti-Semitic comments by Labour activists, including one who was suspended after posting tweets referring to Jews with "big noses" and describing Hitler as a "Zionist God".
The chairman of the Oxford University Labour Club recently resigned, saying a "large proportion" of its members had "some kind of problem with Jews".
Mr Corbyn added: "We are absolutely resolute on this. There is no place for any type of racism of any sort within our party and I will ensure that it is rooted out where it exists.
"But I have to say, it is a very small number of cases over the whole country and we are dealing with it."
Luton councillor Ms Gurbuz suggested her sister may have posted the now-deleted comments on her Twitter account.
The Mail on Sunday reported that she told the Campaign Against Antisemitism: "It was a joint account I had with my sister so I don't know if she's gone out and tweeted that, but I'm absolutely appalled right now."
"Where I live we've got very good cohesion with the Jewish community... I'm absolutely shocked."
A Labour Party spokeswoman said: "Councillor Gurbuz has been suspended from the Labour Party pending an investigation."