Sadiq Khan was elected London's first Muslim mayor on May 6 after defeating Zac Goldsmith.
Khan, who grew up in public housing as the son of a Pakistani bus driver, scored a huge win for the Labour Party; Goldsmith, who represented the Conservative Party, is the son of a billionaire, reports Reuters.
Goldsmith accused Khan, a former human rights lawyer, of sharing stages with radical Muslim speakers and providing "oxygen" for Muslim extremists.
However, Khan insisted that he has opposed extremism and regretted sharing a stage with people who had "abhorrent" views.
Goldsmith insisted that he brought up legitimate questions, but some voters told Reuters that the campaign was "disgusting and slimy."
New York City Mayor Bill de Blasio offered his congratulations on Twitter: "Sending congratulations to London's new mayor and fellow affordable housing advocate, @SadiqKhan."
Goldsmith congratulated Khan on Facebook and thanked "the hundreds of thousands of people who trusted me with their votes."
"Back then, I never dreamt that someone like me could be elected as Mayor of London, and I want to say thank you to every single Londoner for making the impossible possible today," Khan said of his childhood during his victory speech at City Hall, notes The Sun.
Khan also mentioned his late father, an immigrant from Pakistan, whom he called "a wonderful man and a great dad."
"He would have been so proud today," Khan added, "proud that the city he chose to call his home has now chosen one of his children to be the mayor."
"I promise to always be a mayor for all Londoners, to work hard to make life better for every Londoner, regardless of your background and to do everything in my power to ensure you get the opportunities that our incredible city gave to me," Khan told a cheering crowd.
In a recent interview with GQ, Khan was asked about his Muslim faith and said: "I am a dad, a husband, Londoner, Asian, British, Muslim. I never run away from my faith but I don't proselytize."