In a poll of passengers, the BBC found one in five people travelling on a tram did not have a ticket.

Passengers say the conductors have not been coming to collect their fare before they arrive at their stops.

Officials have blamed the rush to try out the new service and say they expect to initally lose money as a result.

Electronic machines

Tram bosses have also said they expect to lose about 5% of revenue due to fare dodgers, once the teething problems have been resolved.

Passengers have criticised the service for not having electronic ticket machines and barriers.

But the firm is adament that conductors, even if they are slower at issuing tickets, are the best way of serving customers.

Colin Lea, spokesperson for NET, said: "We don't want to think of a different system.

"What we'll do is bring in more conductors, we think the system is right.

"Conductors are certainly going down very well with the public, they like a friendly face on the tram.

"It's good for safety at night and getting the right change.

"Conductors is definitely the right policy rather than ticket machines."

Managers also said it was cheaper to account for the missed fares rather than installing electronic machines to issue and stamp tickets.