Members of the union Unison have threatened strike action over plans to introduce performance-related pay and other conditions for office staff.

Operator of the system, Nexus, wants to introduce a new, non-compulsory, scheme for 450 white collar staff.

Staff do not have to join the scheme, but Unison says the new conditions would mean workers would be worse off in the long-term.

It is also annoyed at what it says was a lack of consultation about the new scheme.

Nexus also wants to extend its random drug and alcohol testing programme to all its 1,000 staff.

'Sort things out'

John Young, Unison branch secretary, said: "It is the manner of the way they have gone about it, without any proper consultation at all.

"We were hit with a raft of proposals - covering job evaluation, performance related pay, conditions of service, redeployment policy, and on the tail end was the drugs and alcohol policy."

Nexus spokesman Andy Lee said they had been inviting the union to talks over the past two years.

He said: "It seems a little bit strange to us that Unison should start to ballot for industrial action on things they are not prepared to negotiate on.

"So lets get into talks next week and get things sorted out."

In autumn 2002 there was a threat of a six-day strike on the Metro by Unison members over pay for control room staff. It was called off when agreement was reached.