The recently retired head of economic development company Liverpool Vision will advise council leader Cllr Joe Anderson and his chief executive David McElhinney for two days a week over the next three months.
Gill's brief will include city region governance, proposals for a city region local enterprise partnership, major regeneration projects, economic policy and the Jessica European Investment Bank fund for urban investment projects.
Anderson said: "Jim's guidance and advice will be important and extremely valued as we start the restructure of the council's senior management team.
"His role will be to give us guidance and support on more strategic and long term policy, to complement the day-to-day management role being carried out by the interim director of regeneration, Nick Kavanagh. I'm very grateful to Jim for putting his retirement on hold for the next few months to help us out."
Gill, 61, retired in July from Liverpool Vision, the economic development company partly funded and controlled by the council. He was replaced by Max Steinberg, formerly chief executive of Regenerate Pennine Lancashire.
Gill said: "I said when I retired from Liverpool Vision that I had developed a strong attachment and commitment to Liverpool.
"I'm delighted to have the opportunity to continue my relationship with the city and to contribute what I can to its future success."