Theresa May has given her strong backing, as has every living former prime minister, to plans for a Holocaust education centre on a site next to the Houses of Parliament.

Proposals for the memorial and museum, in Victoria Tower Gardens next to the River Thames in central London, have sparked a backlash because of the loss of green space and trees their construction would entail.

A “Save Victoria Tower Gardens” campaign is urging members of the public to protest, and the International Council on Monuments and Sites (Icomos), which advises Unesco on world heritage sites, has objected, warning that the proposal would have a “massive visual impact”.

But the prime minister will on Tuesday insist that building the centre on the site has an important symbolic meaning.

The centre is to be built in Victoria Tower Gardens next to the River Thames in central London. Photograph: HayesDavidsonAdjaye Associates & Ron Arad Architects

“By putting our National Holocaust Memorial and Education Centre next to our parliament, we make a solemn and eternal promise that Britain will never forget what happened in the Holocaust,” she said.

“Seeing this through is a sacred, national mission. In the face of despicable Holocaust denial, this memorial will stand to preserve the truth forever.”

The prime minister’s words will be played at a ceremony to mark the annual British Heroes of the Holocaust award, alongside supportive video statements from her predecessors David Cameron, Tony Blair and John Major.

Blair said: “Antisemitism and hate did not end in 1945. Unfortunately today some of this poison is back from the political fringe to parts of the political mainstream. So it’s absolutely right that this new national memorial is situated right next to parliament. So we can show what happens when racism and prejudice go unchecked.”

Another computer-generated image of David Adjaye’s design for the holocaust centre. Photograph: Adjaye Associates & Ron Arad Architects

The British Heroes of the Holocaust award will be awarded posthumously to two women, Joan Stiebel and Lady Rose L Henriques, by the communities and local government secretary, James Brokenshire.

Stiebel was responsible for making travel arrangements to bring 1,000 underage Jewish orphans from Nazi concentration camps to the UK, and remained involved with the group until her death in 2007.

Henriques, with her father James Loewe, was the warden of the St George’s Jewish Settlement in Stepney, east London. When the war ended she went to Germany where she worked alongside a number of Jewish welfare groups at the former Bergen-Belsen concentration camp, and then at the nearby displaced persons camp. She died in 1972.

Brokenshire said: “We can draw real inspiration from the women awarded British Heroes of the Holocaust medals today. They refused to turn away and leave it to others to do the right thing. Instead they took on personal responsibility and their courage and human compassion saved many lives.”

The government has committed £50m to the building of the Holocaust education centre, which has been designed by a consortium ofarchitects, led by David Adjaye.

Several changes to the design have been made to placate critics, including redesigning the entrance pavilion and opening up a new view through to parliament from the park’s playground.