James Morris is standing down as chief executive of the Localis thinktank following his election to the House of Commons.
Mr Morris was returned after 6 May as the Conservative MP for Halesowen and Rowley Regis with a 2,000 majority.
Localis says a process to find a replacement is underway.
Merrick Cockell, chairman of the board, said: “As Chief Executive he has set Localis on a new path, stimulating debate and thinking about decentralising power. With perfect timing, he now has the opportunity to pursue localism in Parliament.”
On 11 May, Chris Leslie, who won Nottingham East for Labour at the general election, resigned as director of the New Local Government Network (NLGN).
Iain Roxburgh, chair of the NLGN board, said that the process to find a replacement by the end of the summer was underway and deputy director Anna Turley would be acting director in the meantime.