Douglas Alexander said Labour would miss Mr Johnson "big contribution" but was united in its deficit reduction policy under new shadow chancellor, Ed Balls.
Mr Balls and Labour leader Ed Miliband agreed that cuts were needed but the coalition was going too fast, he added.
Mr Miliband and Mr Balls do not differ on the crucial issue of how quickly to reduce the deficit despite the fact that Mr Balls called for a much slower pace of spending cuts than his then rival during last year's leadership contest.
However, Mr Alexander urged Labour to provide a credible alternative to the government's plans for £81bn cuts over the next four years.
"We are determined to pull together, leave behind some of the problems of the past, and start anticipating what questions the public will be asking of us over the next three or five years.
"All the headlines are about people being angry and indignant. I think the real challenge for Labour is not just to express anger but to offer answers."
Courtesy of the BBC