BBCNews said:Row over new penalties on trains
Staff in dispute with a train operator are refusing to issue penalty fares due to be introduced this weekend.
Union members at Silverlink, which runs trains between London, Bedford, Milton Keynes and Northampton, said an offer to work new systems was not acceptable.
"Members are angry as penalty fares put them at risk and hit commissions on tickets," Rail Maritime and Transport union general secretary Bob Crow said.
Silverlink was not available for comment on Monday.
Thirty-nine out of 70 union members at Silverlink voted for industrial action, Mr Crow said.
Call for negotiation
Silverlink abolished its penalty fares system in 1999 and since then passengers without tickets have just been asked to purchase one when discovered by inspectors.
The train operator now wants to reintroduce a penalty fares system but the union said it is doing this without consulting them on a fair payment for the inspectors asked to implement it.
Mr Crow said: "We want to negotiate on the system to ensure our members do not miss out on ticket commissions if penalty fares are imposed.
"We also want to ensure safety systems are in place to protect them as passengers will not be pleased to have to pay a penalty for not purchasing a ticket.
"If the company really believed it could get away with that without offering a penny piece in return, our members have told them in no uncertain terms that they were wrong.
"Silverlink now have a simple choice: They can either get back round the table and negotiate sensibly or they can issue their penalty fares themselves - because our members certainly won't be doing it."