The samples will be sent for analysis and used in a prosecution

The packs will be issued to staff on board Northern Rail trains, which cover Cumbria, after statistics showed a growing number of assaults on workers.

The "spit kits" will enable staff to gather a DNA sample from items which an attacker has been in contact with.

Once sealed in a tamper-proof bag, the evidence will be passed to British Transport Police for analysis.

Staff working late-night services are facing the worst cases of anti-social behaviour.

'Behave sensibly'

Craig Johnston, a guard with Northern Rail and a local official with the RMT union, said staff were supportive of the measures.

He said: "We have members of staff who have been spat at, it has happened to me, so we are very supportive of the introduction of this kit with the proviso that staff are trained sufficiently to use it.

"It is one of a number of initiatives - all conductors now have mobile phones so we are in constant contact with our control centre and police.

"As long as it is used sensibly and the correct procedures are in place to use it, it is another tool in our armour.

Mr Johnston said the company was already running a poster campaign warning passengers of the dangers of legal action if they do abuse staff.

He said: "I don't have a problem with people having a few drinks and using trains, but we are asking people to behave sensibly."