London's mayor has backed down over comments he made about the employment on the Tube of a convicted terrorist.
Mostafa was jailed in Yemen in 1999
Ken Livingstone had earlier said he was "happy" for Mohammed Kamel Mostafa, son of jailed Islamic cleric Abu Hamza, to be working on the underground.
Mostafa, 25, was jailed for three years in Yemen in 1999 for plotting a bombing campaign.
But the mayor said because Mostafa had failed to declare his convictions, his employers "are correct to dismiss him".
"Mr Mostafa has convictions in Yemen," he said. "These must be taken into account.
"They should have been brought to light by those doing the security checks, the failure to do so must be investigated.
"I was not aware of this man's convictions at the time of my press conference this morning, only of his family.
"It is clear that anyone who has been involved in terrorism in any form cannot be employed on the London Underground."
Earlier, during a press conference at City Hall, Mr Livingstone appeared to back Mostafa's employment on the London Underground.
"Has he broken any law here in Britain? [No, so] we are happy to have him working for us," he said.
Mostafa was convicted of plotting to sabotage economic and tourist sites in Yemen in August 1999, when he was 17-years-old.
He has recently been working as a labourer for a company contracted to Tube Lines, one of London Underground's maintenance firms.
It is understood Mostafa's previous convictions were not brought to light during his recruitment and he has since been dismissed.
The Tube's vetting procedures were supposed to have been intensified since the 7 July bombings, but Bob Crow, head of the RMT, has called for a review of the Underground's current recruitment procedures.
Labour MP Andrew Dismore said applicants with terrorism-related convictions anywhere in the world should not be eligible for employment on the Underground.
"The key point here is that terrorism is an international crime," he said.
"Bearing in mind what happened on 7/7, he should not have been working on the Underground."
Mostafa's father, Abu Hamza, was jailed for seven years in February for incitement to murder and inciting racial hatred.