Statistics reveal more than 500 assaults on Northern Line staff were committed over the past 18 months - around ten a week on the so-called misery line' alone.

Commuters using the service are also the third most likely to be assaulted in London, with 57, according to figures from Transport for London (TfL) covering the same period of time.

Of the 531 attacks on staff, eight were against off-duty personnel. The second most targeted London Underground employees work on the Piccadilly Line, with 363 attacks. Jubilee Line staff suffered 300 attacks.

Although there is no breakdown to show the worst-hit Northern Line station for staff assaults, TfL confirmed that of 13 Northern Line stations in the borough of Barnet, there were 85 attacks in the 12-month period between March 2005 and March 2006.

The figures were published following a question to Mayor of London Ken Livingstone from London Assembly member and Barnet councillor Brian Coleman.

Calling for a tough stance on people who attack Tube staff, Mr Coleman said: "I travel on the Northern Line regularly and, while it is beset with problems and highly frustrating, the under-performing service is absolutely no excuse for assaulting London Underground staff, and there should be a zero-tolerance policy in place to punish offenders."

Mr Coleman also called for TfL to use its recently granted powers to issue ASBOs to remove troublemakers' from the transport service, although TfL is yet to apply for any ASBOs.

A spokesman for TfL said: "In the last year, staff assaults dropped by 4.5 per cent and assaults on passengers dropped by 17 per cent. The vast majority of these incidents relate to verbal abuse - obviously this is something we still take very seriously.

"The Tube is, overall, an extremely safe form of public transport. Three million journeys are made each day on the Tube. The network is a safe environment."