Conservative leader David Cameron has highlighted what he called Labour's "broken society" while campaigning in the Glasgow East by-election.
Mr Cameron and former Tory leader Iain Duncan Smith joined candidate Davena Rankin in the constituency on Monday.
Labour, which has yet to choose a candidate, said it was getting people off benefits and into work.
The SNP campaign launched with a call for action on rising energy costs. The Lib Dem campaign launches on Tuesday.
The 24 July by-election was triggered by Labour MP David Marshall's resignation on health grounds.
During his campaign visit, Mr Cameron said it was the Conservative's mission "to heal the wounds of poverty, crime, social disorder and deprivation".
He said social breakdown in Glasgow East was simply an "extreme version" of what could be seen elsewhere and highlighted the high level of welfare dependency and knife crime.
"This is the broken society by-election," said Mr Cameron.
"It comes in a place where the people are shouting 'Gordon Brown, wasn't Labour supposed to end this degrading poverty?'.
"It comes at a time when the country is asking 'What is going on with the knife crime and violence on our streets?'."
Mr Cameron said the Conservatives had a clear plan to foster social cohesion while they attempted to rebuild the economy and improve the NHS.
"We can and will bring hope and aspiration to places where there is resignation and despair," he said.
"Whether it is knife crime or any other symptom of our broken society, we will repair the damage by treating not just the symptoms, but the causes too."