Ed Miliband sought to keep the pressure on the government over the resignation of Liam Fox during prime minister's questions on Wednesday - but was accused of jumping on a "bandwagon" by a tetchy David Cameron.
During a tense session, David Cameron told the Labour leader that the former defence secretary had admitted to mistakes: "I do think it is worth actually recognising that in this case the secretary of state for defence recognised that he made a mistake, acknowledged that he broke the ministerial code and he resigned: that is not something that happened in the last 13 years."
But Miliband demanded to know how he allowed the breaches of security to happen, saying: "This week of all weeks, show a bit of humility. And the truth is, we still don't know the full facts about this case, about the money trail, about who exactly in this government met Mr Werritty.
"And it is becoming clear that there's a network of individuals who funded Mr Werritty some with close links to the Conservative party and others with members of the Cabinet.
"Now, given that he says he knew nothing about the arrangements of the former defence secretary, can he give us now a categorical guarantee that over the last 18 months no other government minister had been engaging in similar activities?"
Instead of a clear answer, the prime minister outlined past Labour's scandals: "Cabs for hire, passports for favours, mortgages for mates, dodgy dossiers, smearing opponents, good days to bury bad news."
Cameron added: "If you're going to jump on a bandwagon, make sure it's still moving."
Labour also attacked the prime minister over the economy, saying that there had been 22 press releases about the regional growth fund, but only two businesses had been helped by it.