The Scottish First Minister said Labour’s decision not to oppose the “ideological assault” on low-paid workers showed the party had “lost its sense of purpose”.
While SNP MPs voted against the Welfare Reform and Work Bill, the majority of Labour MPs abstained - although 48 rebels did defy interim leader Harriet Harman and vote against it.
Ms Sturgeon, the SNP leader, said: “If Labour had voted with the SNP against George Osborne’s assault on those on low incomes, then the Tories could have been beaten last night.
“Instead Labour sat on their hands.”
Ms Sturgeon said she was “sadly not” surprised by the party’s decision to abstain, adding: “It really does beg a fundamental question, if Labour is not about opposing a Tory government that is waging an ideological assault not on skivers who don’t want to work, but on people who are working hard on low incomes, if Labour is not about opposing that, what is Labour for?
Ms Sturgeon made the comments as she campaigned in Glasgow, where four council by-elections are due to be held on August 6.
Forty-eight Labour rebels have defied the party leadership to vote against the Government’s welfare reforms.
Leadership contender Jeremy Corbyn was among the MPs to ignore interim leader Harriet Harman’s call for them to abstain in the Commons second reading vote on the Welfare Reform and Work Bill.
Former Labour Cabinet minister and Sheffield MP David Blunkett said the party was suffering “emotional trauma” in the wake of the election defeat.
The revolt is the largest rebellion within Labour ranks since December 2013, according to Nottingham University’s Professor Philip Cowley.