Weldon, a former Bank of England employee and BBC Newsnight economics correspondent, joined LGIM in February to boost its multi-asset team by sharing views on market strategy, idea generation and investment research.
He took to Twitter on Tuesday to announce he is leaving LGIM at the end of the week and “joining the Economist to write about the British economy”.
An LGIM spokesperson confirmed Weldon’s departure “to pursue future media opportunities”.
“He leaves LGIM on very amicable terms, so we remain in touch and wish him well for the future,” they added.
Weldon has spent time at the Bank of England, as head of research at the Resolution Group and as a partner at Senhouse Capital.
He was appointed BBC Newsnight’s economics correspondent in 2014 and was economics adviser to the leader of the opposition, Harriet Harman, in 2010, as well as a senior economist at the Trades Union Congress.
Weldon’s appointment at the BBC was met at the time with uproar from certain Conservative MPs, including Andrew Bridgen, because of his Labour Party affiliation and his perceived lack of journalistic experience.