The ballot will involve the railways 'white collar' workers

Officials from the Transport Salaried Staffs Association (TSSA) rejected a 3% pay offer and planned pension changes as part of a deal from Network Rail.

Members will be asked over the next few weeks if they support a ballot on strikes or action short of a walkout.

Members of the Rail Maritime and Transport Union are also balloting.

The RMT union has already asked 7,000 workers in Network Rail to vote on striking over similar concerns.

The two unions hope to co-ordinate industrial action to create more disruption and have a greater impact.

The possible strike would be the largest action in the industry for a decade.

'Rock bottom'

The TSSA said morale at the company was at "rock bottom" following a series of redundancies last year among white collar staff.

Our members living in London face the same costs so why should they get less pay? Gerry Doherty, TSSA General Secretary

The union complained about the new pension scheme and said it was angry about the level of allowances paid to staff based in London.

General Secretary Gerry Doherty said Network Rail had given some operational workers in London a 10% increase in allowances but administration workers received nothing.

"This offer is divisive and derisory", he said.

"Our members living in London face the same costs so why should they get less pay?

"Morale among staff is at rock bottom and plans to close the final salary pension scheme to new entrants will be the last straw for many."

The RMT said the pay deal offered by Network Rail was worth 3% and the worst in the railway industry, while a new pension scheme was also inferior.

Network Rail said the threat of industrial action by the RMT was "astonishing".