The 45-year-old Conservative party MP was a key ally of former British Prime Minister David Cameron and lost his frontline Cabinet job in the post-Brexit reshuffle when Theresa May took charge of Downing Street in July 2016.
Now he is to remain an MP for Tatton in Cheshire as he edits the newspaper four days a week.
"Growing up as a Londoner, I've always known that the Evening Standard is an institution that plays a huge part in the life of the city and its people," Osborne said as he addressed journalists at the newspaper today.
"We will judge what the government, London's politicians and the political parties do against this simple test: is it good for our readers and good for London? If it is, we'll support them; if it isn't we'll be quick to say so."
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The newspaper said its schedule would enable Osborne to "continue to fulfil his other commitments, including as an MP; giving him the time to vote and contribute in Parliament in the afternoon after the paper has gone to print and be in his constituency".
"It's taking multi-tasking to an extreme level," he tweeted.
Former Labour leader Ed Miliband joked on Twitter that he would "shortly be announced as editor of Heat magazine" while Lib Dem leader Tim Farron suggested his next job would be as editor of the adult comic Viz, BBC reported.
The owner of the daily newspaper, Evgeny Lebedev, said Osborne was "London through and through" and he was confident that the MP was "the right person to build on the fantastic legacy of Sarah Sands", who has left as editor to join the BBC.
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