Senior Liberal Democrats have not entered the row which has seen David Cameron back Chancellor George Osborne's comments that the case prompted "wider questions about our welfare system."
Mr Alexander said: "The Philpott case is an individual tragedy. Children have died in that case.
"I think that is where we should let that case lie. I would not want to connect that to the much wider need to reform our welfare system."
More top news
US-backed rebel fighters say they have taken control of a key airbase near the so-called Islamic State's stronghold of Raqqa.
A primary school has taken action after pupils brought in an variety of "worrying" packed lunches - including a two-day-old McDonalds.
A 30-year-old man was arrested in Birmingham on Sunday on suspicion of preparing terrorist acts.