A leaked Home Office document has revealed that five intelligence reports since 2006 showed that a cleaning company used by Parliament employed South Americans working illegally on false passports and identities.
The Tories accused ministers of covering up a "catastrophic failure of security" after an illegal immigrant, a Brazilian woman, was caught trying to gain entry to Parliament by using another person's security pass.
Her employer, Emprise Services, said that it would redouble its efforts to spot identity theft and passport fraud.
Damian Green, the Tories' immigration spokesman, said: "Home Office ministers still haven't learnt that covering up these successive scandals only makes it worse in the long run."Reuse content