Whatever the circumstances, and irrespective of your background, profession, age, colour or gender, violence is not acceptable

Mike Brown, London Underground

Figures show that Underground staff are almost three times as likely to be assaulted than they were 25 years ago.

An LUL spokeswoman said: "This is a growing problem and the upshot is that we are seeking legal advice to establish what further measures we can take against people who physically assault our staff.

"We don't want customers like that on our system and that's why we are looking at whether we could ban them from the Tube and, if so, how we can do so effectively."

Referring to Mr Livingstone, she said: "Over the past 18 months or so it has become clear that the constant Tube bashing from the mayor has not helped improve public empathy towards front-line Underground staff."

Mr Livingstone blamed for "tube bashing"

Mr Livingstone said: "The poor performance of the Underground under the preparations for privatisation is the major cause of increasing public anger and it's no good anonymous spokespeople pretending otherwise.

"The current LUL management is responsible in the last 12 months for no less than a 43% increase in peak period train cancellations."

Consultant anaesthetist John Nelson, 37, escaped jail but was fined �1,000 for assaulting staff at Kennington station, and ordered to pay �1,500 compensation and �6,300 costs.

In future, those involved in such incidents who are successfully prosecuted could face being banned from the tube.

'Zero tolerance'

Mike Brown, London Underground's customer services director, said: "We are sending out a clear message to all those who use the Tube that our staff are not fixed targets of abuse and are entitled to carry out their duties without fear of verbal attack or physical assault.

"Whatever the circumstances, and irrespective of your background, profession, age, colour or gender, violence is not acceptable.

"It's a zero tolerance approach. We will always prosecute and now we are looking to see what further steps we can take to keep those people off our system."