Mehdi Hasan has been named political director at Huffington Post UK but will continue to write a weekly column for New Statesman,
The move has seen New Statesman chief political commentator Rafael Behr promoted to the job of political editor.
Hasan, formerly the magazine's senior editor (politics), joined the New Statesman in 2009 and is a former news and current affairs editor at Channel 4.
Editor Jason Cowley said: 'I shall be sorry to see Mehdi leave the staff but he joins the HuffPo with my good wishes.
'Since the NS hired him from a behind-the-scenes role at Channel 4, his development as a writer and broadcaster has been outstanding.
'We shall miss his energy, his ideas – and the office will certainly be a quieter place without him.
'I'm delighted that he will continue to write a column for the New Statesman magazine, which will be his only print outlet.
'Rafael is a first rate writer and journalist, who joined us last summer as chief political commentator, and I know he will excel in his new role."
Commenting on his move, Hasan said: 'I am sad to be leaving the New Statesman after three years but am delighted to be able to continue writing columns for the magazine.
'I've had an amazing spell at the NS – including general elections, coalition governments, London riots and the Arab Spring – but am looking forward to a new challenge at the Huffington Post."
Behr joined the New Statesman as chief political commentator in 2011. Before joining the New Statesman he worked as the chief leader writer for the Observer, as a business reporter for the BBC and for the Financial Times as a foreign correspondent.
Last week the magazine announced deputy editor Jon Bernstein was being promoted to digital director of Progressive Media International, and would be replaced by former assistant editor Helen Lewis.
In his new role Hasan will work alongside political editor Chris Wimpress and reporter Ned Simons, reporting to editor-in-chief Carla Buzasi.
She said: 'I'm delighted to welcome Mehdi to HuffPost UK. A talented and passionate writer, he will make a fantastic director for our political team.
'Politics drills down into the minutia of everyone's day-to-day lives and with so much happening at both a national and global level, it couldn't be a better time to expand our team and the breadth of reports, news and blogs we offer to our growing audience."
Press Gazette, like New Statesman, is part of the Progressive Media group.