Train conductors in Sussex have been spat at, punched and insulted in a spate of attacks during a crackdown on fare dodgers.

Now the RMT union, which represents conductors, is considering holding a ballot over striking on late night services unless security is improved for staff.

There were three attacks on Connex conductors after they asked to see passengers' tickets. Other incidents involving spitting and verbal abuse have been reported to British Transport Police.

Officers are investigating after a conductor was punched by a man when he tried to inspect his ticket on a train at Hastings on Saturday night.

The same evening, a passenger shoved a conductor when he was asked to leave the train after refusing to pay on the Eastbourne to London train at Wivelsfield. Two conductors who spoke to a man without a ticket were assaulted on a train from Bognor to Brighton, which had stopped at Barnham station, near Bognor.

In another incident on Tuesday afternoon, a woman who was asked for her ticket on a Thameslink train from London to Brighton threw the conductor's ticket machine on the floor and stole his mobile phone.

No arrests have been made.

Inspector Mick Morriss, of Brighton Transport Police, said officers had been working with Connex conductors and security staff to patrol trains and catch troublemakers.

He said: "It is a very extreme reaction to people not wanting to pay for their tickets. It is something we have had dealings with for years but it has got a lot worse in the last couple of years. It is a sad reflection on society."

Connex made £250,000 from penalty fares imposed during a zero-tolerance week on fare evasion and insisted it had a zero-tolerance policy towards attacks on staff.

Jim Stevenson, of the RMT in the South-East, said more needed to be done to improve security, including more prosecutions and a faster response from the police.

Eight security guards have been introduced on the Portsmouth to Brighton line after a meeting between rail staff, the RMT and Connex. Conductors said it was not enough and there needed to be guards on other routes.

Mr Stevenson said: "We are being supported on a zero-tolerance policy by Connex, who will go for prosecutions on every occasion where there is evidence.

"There needs to be training for guards to make sure they know how and when to walk away from situations.

"We think Connex and the police have a responsibility and would like to see police on every train but this is obviously not logistically possible. All we can do is tell people in London and Brighton we will not tolerate any assaults on staff and will even take out injunctions to stop them travelling.

"There is still the possibility of a ballot for staff to refuse to work trains at certain times."

A Connex spokeswoman said there had been a 19.4 per cent reduction on attacks on staff on the Sussex coastal route in the last year and £4 million was being spent on better security.