Tyne and Wear Metro operator Nexus hopes to increase its service between Newcastle and Sunderland.

But this could mean halving a Northern Rail service which runs twice-hourly from Sunderland, via Newcastle, to Gateshead's MetroCentre.

The RMT union has condemned the plans, calling them "back-door cuts".

It says it will oppose any proposals to reduce the only rail service to the MetroCentre - Europe's largest shopping centre.

The general consensus is that it would be a good idea to reduce Northern Rail services from two per hour to one per hour on that stretch of track SRA spokesman Jonte Alone

Bob Crow, the RMT's general secretary, said: "The government has tried to give the impression that the amended review would not damage services, yet now we hear that a decision to slash services from Newcastle and Sunderland to the MetroCentre has already been made.

"I have already written to the transport secretary seeking an assurance that there will be no cuts in jobs or rail services, no massive fare increases or line or station closes as a result of this review."

However, the SRA denies that any decision has been made, though it admits the idea of halving the service is being considered.

Spokesman Jonte Alone said: "We have been in discussions with Northern Rail and Nexus, which has put forward a request to run trains every 12 minutes between Newcastle and Sunderland.

"This is a busy stretch of line, which is also used by some freight services.

"The general consensus is that it would be a good idea to reduce Northern Rail services from two per hour to one per hour on that stretch of track to accommodate Nexus's request.

"But no firm decision has yet been made."

Nexus currently runs service between Sunderland and Newcastle every 16-18 minutes.