Beaten London mayoral candidate Zac Goldsmith has made no comment as he left his home.
The Conservative polled second, with 43.2% of the vote once second preferences were counted, making a brief speech at City Hall following the post-midnight announcement.
But he refused to answer any questions this morning.
A “full and urgent inquiry” is being demanded after voters across Barnet were turned away because of a council blunder.
Names were missing from polling lists and residents who attempted to cast their vote were stopped.
People affected were later offered emergency proxy votes.
The leader of the Conservative group in the London Assembly, Gareth Bacon, claimed any lost votes could have affected the allocation of London-wide seats.
To have voters turned away for any reason is completely unacceptable.
We are demanding a full explanation for this abysmal administrative performance.
London Elects and Barnet Council have had four years to plan for this but they both failed to get it right when it mattered and the voting public has suffered.
Newly elected mayor of London Sadiq Khan will announce today he is standing down as the MP for Tooting, reports Simon Harris.
Mr Khan, who won 56.8% of the mayoral vote once second preferences were counted, has been Tooting MP since 2005
Sadiq Khan gave a cheeky wink as he officially accepted the office of mayor of London.
He signed the declaration in front of hundreds of well-wishers at Southwark Cathedral.
Newly elected mayor Sadiq Khan said he "can't quite believe the last 24 hours" as he was sworn in at Southwark Cathedral.
Introduced by Doreen Lawrence, applause erupted as he opened by saying: "My name is Sadiq Khan and I'm the mayor of London."
I'm determined to lead the most transparent, engaged and accessible administration London has ever seen, and represent every single community and every single part of our city as mayor for all Londoners.
I promise you that I’ll always do everything in my power to make our city better.
Doreen Lawrence, the mother of teenager Stephen Lawrence who was murdered in 1993, has hailed the election of Sadiq Khan as mayor.
Describing today as a "glorious day" as she introduced him for his signing in at Southwark Cathedral, she added:
I never imagined in my lifetime I could have a mayor of London from an ethnic minority background. It is an amazing sign of how far our city has come.
London is a city that not only tolerates but celebrates diversity.
A city that’s chosen unity over division and hope over fear. A city that’s chosen a mayor for all Londoners.
Southwark Cathedral is the setting for Sadiq Khan's singing in as the new mayor of London, with politicians and even celebrities out in force.
Newly elected London mayor Sadiq Khan has left for his first day in his new job pledging to be a "mayor for all Londoners".
Saying he was "tired" after weeks of campaigning and a result which came after midnight, he told reporters outside his home his priority was "to try to get to the office".
I look forward to working with everyone to make sure I can be a mayor for all Londoners.
The Islington North MP and Labour leader was spotted on Google street view riding his trademark red bikeRead the full story ›
Labour leader Ed Miliband defended his party's plans to use a mansion tax to pay for nurses in Scotland, if he wins the election. 85 per cent of those affected by the tax would be in London and the South East. But Mr Miliband insists the capital will also benefit.