One in 20 UK adults do not believe the Holocaust took place, a survey reveals, while one in 12 believes the scale has been exaggerated.

Almost two-thirds of respondents (64 percent) either could not say how many Jews were murdered or “grossly” under-estimated the number, a survey of more than 2,000 people by the Holocaust Memorial Day Trust (HMDT) found.

Five percent fell into the “Holocaust denial” category, while eight percent said it had been exaggerated, the survey reveals. At least six million Jews died.

“Such widespread ignorance and even denial is shocking,” said HMDT chief executive Olivia Marks-Woldman. “Without a basic understanding of this recent history, we are in danger of failing to learn where a lack of respect for difference and hostility to others can ultimately lead… We cannot be complacent.”

On Sunday, hundreds of thousands of people, including survivors, politicians and members of the public, will gather to mark Holocaust Memorial Day and remember its six million Jewish victims.

Today is Holocaust Memorial Day. Together, we must learn from genocide, challenge prejudice and create a better future. Watch and share our film for #HolocaustMemorialDay pic.twitter.com/llk5GS3Znh — Holocaust Memorial Day Trust (@HMD_UK) January 27, 2019

More than 11,000 activities are expected to take place, while ceremonies will be held in London, Scotland, Wales and Northern Ireland across the day.

UK Communities Secretary James Brokenshire, who will be speaking at Sunday’s event, said: “It remains essential now as ever to remember the Holocaust, to understand why it happened and to learn the stark lessons it gives.

“We must never forget where hatred and bigotry can lead.”

He added: “This Government is clear that anti-Semitism has no place in our society and we all have a role to play in confronting hatred and extremism whenever and wherever it occurs.”