Hate speech is poisoning Irish society, according to the Labour leader.
Brendan Howlin has also accused the Taoiseach of sending "mixed messages" on the issue.
Speaking at his party's annual conference in Mullingar last night, Deputy Howlin suggested that a "new toxic racism" has entered Irish politics.
The Labour leader argued: "Let’s call it what it is.
"From protests against asylum seekers, through to a presidential candidate making disparaging comments about Travellers.
"Longstanding taboos have been broken."
Deputy Howlin added: "We've seen what happened elsewhere, but it doesn't have to happen here.
"Labour will stand for equality and against the hate speech that is poisoning society. Leadership is needed on this issue, but the Taoiseach has sent mixed messages at best."
He pointed to one in eight people living in Ireland having been born in another country, as well as one in seven children and young people having one or both parents from another country.
The Labour leader noted: "One in 20 are visibly different, from an African or Asian background.
"These are our children, our people, our equals."
Mr Varadkar recently faced criticism for comments he made about immigration, claiming illegal immigrants from Georgia and Albania were a “big driver” behind a rise in the number of asylum seekers in the country.
The Irish Refugee Council responded by saying "generalised assumptions that countries are de facto safe are dangerous" - pointing to human rights organisations reporting issues in both the named countries.
Separately, the Taoiseach said on Wednesday that there was a need to call out "scaremongering" about asylum seekers, noting there are people attempting to exploit local concerns for 'political, personal or - in some cases - racist reasons'.