An investigation is under way after a London tube worker was found to be responsible for posting a series of racist and anti-Muslim messages on his Facebook page.
Train engineer Martin Aitken posted several offensive jokes about Asians, Muslims and disabled people on the site dating back to 2010.
After he was approached by the Evening Standard about the messages, Aitken said the revelation was "going to jeopardise my job".
He told the newspaper that he did not hate Muslims and was not a racist as his "best mate is Jamaican".
One post, from March 2010 read: "Did you know that in the time it takes to clap your hands, a Pakistani will die somewhere in the world. All together now - 'If your[sic] happy and you know it'".
Other posts include jokes about disabled African children, assaulting Asian people and a claim that Muslims would not be "hated as much if they made more of an effort with personal hygiene" and "didn't burn poppies".
A Tube co-worker told the Evening Standard: "The content posted on Mr Aitken's Facebook timeline appears to demonstrate a deep-seated hatred for anyone different.
"He is using social networking sites to promote racism and his personal hatred of Muslims."
Aitken added he has deleted his Facebook account and apologised for the posts. He said: "It is stupid. I did not see the offence it could have caused.
"I overlooked the fact I am offending people and I apologise."
A spokesman for Transport For London said it would investigate.
"TfL expects its staff to adhere to the highest possible standards and will not tolerate bigoted and abusive behaviour from staff," he said.
"The content of these posts has been brought to our attention and, in line with TfL's employment policies and London Underground's guidelines for the use of social media, we will be investigating this issue fully."