Shell is now on the hunt for Welch's replacement to take on the role when he leaves at the beginning of May.
A Shell spokesman confirmed the group is looking internally and externally to fill the role, which reports into V-P of external relations and policy Robin Aram.
Welch's post in the UK involves overseeing social investment (including community relations and CSR) government relations, and corporate affairs.
He is supported by a team of seven.
Welch, who was unavailable for comment as PRWeek went to press, has led some of Shell's high-profile CSR projects, including youth business grant and training initiatives STEP and Livewire. He also helped lead Shell's comms efforts through the fuel crisis of 2000.
It is understood the advisory post he is set to take in the US is the first of its kind within the group.
Welch was formerly private secretary for Michael Heseltine during his tenure as president of the board of trade and secretary of state for trade and industry, from 1992 to 1994.
Shell appointed Mary Jo Jacobi as V-P of external affairs in September, just months after Malcolm Brinded was hired as director of planning, environment and external affairs in June (PRWeek, 14 September 2001).