Gordon Brown paid tribute to the "selfless humanity" of Britons who helped save Jews and other persecuted groups during World War II as they were honoured at Downing Street.
The Prime Minister announced the creation of the new Hero of the Holocaust award last year on a visit to the former Nazi concentration camp at Auschwitz.
Two surviving recipients, Sir Nicholas Winton and Denis Avey, were given their medals in person while others were recognised posthumously.
Sir Nicholas Winton, who is now 100, organised the rescue of 669 mainly Jewish children by train from Prague in 1939.
Mr Avey, 91, exchanged places with a Jewish inmate at Auschwitz while he was a prisoner of war - gathering facts about conditions and helping an inmate survive by sharing supplies.
Speaking at the reception, Mr Brown said: "I want, first of all, to pay tribute to all our 28 British heroes of the Holocaust who we honour today for their compassion, resilience and for their great bravery.
"To those with us like Denis Avey and Sir Nicholas Winton, and I welcome both of them here, they are with us today and I have already talked to them. Denis whom I met on Holocaust Memorial Day, helped a German Jew survive Auschwitz and Sir Nicholas, who rescued more than 600 children from Czechoslovakia, single-handedly spiriting them away to Britain by train.
"To those who have gone before us who have equally inspiring stories - and many of their relatives are here today - I want to say how much we hold in awe everyone who is a British hero of the Holocaust.
"It was the extraordinary acts of ordinary people that sustained those suffering the greatest evil our generation has known. It is right that today we recognise that heroism."
He added: "The Holocaust is modern history's darkest chapter. It is the most grievous example of degradation and depravity by men and women to men, women and children. It is against that background that the courage of those we recognise today, who risked their lives to save others, stands out all the brighter."
The event was announced after a long campaign by the Holocaust Education Trust - backed by MPs - for the Holocaust heroes to be awarded MBEs and OBEs posthumously. Mr Avey, from Bradwell, Derbyshire said: "I am overcome, totally overcome. I have humility in receiving it, but I am accepting this award on behalf of myself and my friends, who I helped and who helped me in Auschwitz. I'm so glad this has come about.
"My philosophy is as Albert Einstein once said that the world is an unhappy place, but there is none so evil as those who look on and do nothing."
Sir Nicholas, from Maidenhead, added: "I was in the right place at the right time with the right knowledge about what was going on, so I was able to do all that I did. The Germans were eager to find out what I was doing.
"There were plenty of people who did an enormous amount at the time. Luckily what I did turned out right, it could have all gone wrong.
"My job was to find families who would take the children when they arrived in this country. It was a lot of hard work, but I had a lot of people who helped me."
Post-humous award recipients
• Mills & Boon author Ida Cook and her sister and Louise. The opera-loving sisters from London smuggled British visas to Jews while attending recitals in Europe before the war and brought their valuables back to the UK. Their nephew John Cook, 63, of Huntingdon, Cambridgeshire, said: "They used to stay in the best hotels where the Nazi officials were, rubbing shoulders with Goering and Himmler and they once saw Hitler from behind. "They would bring the belongings to the hotels and sew in British labels. It was very risky, if the Germans had found out they would have been in serious trouble."
• Sr Agnes Walsh of Hull who sheltered a family in her convent in France. She died in 1993 aged 97. Speaking about her actions, Sr Marie Raw, 67, of the Sisters of Charity of St Vincent de Paul, of Mill Hill in north London, said: "To help one person is a great achievement. For Sr Agnes and the other sisters they would have done this without a second thought. They would have seen a family in need and responded to that need."
• Bertha Bracey. A Quaker who lobbied tirelessly about the plight of the Jews in Germany and was pivotal in setting up the Kindertransport which brought 10,000 children to England. Her great niece Pat Webb, 73, of Northampton, said: "I'm just sorry she is not here. She was a very modest sort of lady. She was instrumental in helping Jewish children get out of Germany by arranging with a lot of English families to take the children. "She said it did not matter what religion they were, they were all children who were going to end up in the concentration camp."
• Sofka Skipwith. A Russian aristocrat who lived her later years in Cornwall, she helped Polish Jews escape and saved the life of a newborn baby by smuggling him to the Red Cross. Her granddaughter Sofka Zinovieff, 48, of Greece, who has written a book the Red Princess on her relative's actions after being given her diary said: "She wrote letters on cigarette papers hidden in capsules sent through the resistance saying they must do something to help the Jews. "She also helped smuggle a baby by wrapping him in a Red Cross box and in the dead of night passing him under the barbed wire to give to the resistance, who looked after him until the end of the war when he was sent to Palestine."
• Henk Huffener of Guildford. As a Dutch citizen during the war he smuggled Jews out of Holland to Switzerland and Spain. He moved to England in 1950. He died three years ago aged 83. His daughter Jo Huffener, 48, of Guildford, said: "I am so proud. He would have been so happy to have had his work and that of his family in Holland recognised. He took Jewish children out of Amsterdam and helped to get them through to the resistance and out of the country safely." His other daughter Clare Haddad, 54, added: "My father was fearless and used outrageous audacity to fool the Nazis. He used to listen in on their conversations to obtain information to pass on to the Allies."
• Major Frank Foley of Somerset saved more than 10,000 people at great personal risk by issuing false visas to Jews while working as a spy in the British embassy in Berlin. His great niece Patricia Dunstan, 78, of Helston, Cornwall, said: "I have no other feelings but extraordinary pride. He was an M16 officer working under cover as a passport control officer in Berlin. He managed to get all these people out and rescue them; they would have been killed or shot. He was extremely brave. He couldn't see these people go to the labour camps. He even went into the camps and got prisoners out."
• Albert Bedane. A physiotherapist in Jersey who hid people in his cellar while he treated Nazi soldiers in his clinic above.
• Sgt Charles Coward of Edmonton. Used his position as the Red Cross liaison for British prisoners of war at Auschwitz to smuggle food and contraband to Jewish inmates and to smuggle himself in to witness conditions.
• Jane Haining of Dunscore, Scotland. Despite the outbreak of war, she returned to the Jewish orphanage in Budapest where she worked. She was arrested in 1944 and died in Auschwitz.
• June Ravenhall of Warwickshire. Housewife and mother of three who sheltered a young Jew in her home in Holland despite her husband being taken to a prison camp - never to be seen again.
• Princess Alice of Greece. The mother of the Duke of Edinburgh, she organised shelters for orphans and sheltered three Jewish women when Greece was occupied.
• Louisa Gould, Ivy Forester, Harold le Druillenec of Jersey. The siblings sheltered Russian prisoners of war and taught them English. All three were arrested. Louisa died at Ravensbrueck camp and Harold was the last surviving British citizen at Belsen.
• Stan Wells, Alan Edwards, George Hammond, Roger Letchford, Tommy Noble, John Buckley, Bill Scruton, Bert Hambling, Bill Keeble, Willy Fisher. The British prisoners of war saved the life of 15-year-old Jewish girl Hannah Sara Rigler, who escaped the death march outside Danzig while her mother and sister perished. Sara is still alive and lives in New York.