Margaret Aspinall, chair of the Hillsborough Family Support Group, said Ed Miliband's action of posing with The Sun was a "stupid thing to do".
Miliband apologised after being criticised for failing to take account of continuing fury over the tabloid's coverage of the Hillsborough disaster.
But his apology comes "a bit late", she added.
Mrs Aspinall, attending the inquest into the death of her son James at the Hillsborough inquests in Warrington, said: "Common sense should have prevailed.
"I can't understand the insensitivity of what they have done, they didn't show any common sense.
"They know the families have got enough to get through right now, they know the feelings of the people, not just in Liverpool, it has spread everywhere.
"At this moment in time, it was a stupid thing to do. You have got to think about all the people it affected."
More top news
A mother has been arrested on suspicion of attempted murder after her three young children were found with their throats cut.
Ex-Cuban leader Fidel Castro has broken his silence over Cuba and the United States' attempts to repair diplomatic relations.
David Cameron has pledged to reduce the annual benefits cap to £23,000 "within the first few days" of a Conservative election win.