Connex was stripped of the franchise last June

The Rail, Maritime and Transport union (RMT) said figures showed up to 40% of all workers in the region used South Eastern Trains to travel to work.

The union argued the service should be brought "in-house" to give the public sector a chance to prove itself.

A number of bidders are currently competing for the new franchise.

'Efficient public hands'

South Eastern Trains took over the operation of services in Kent, East Sussex and south east London after the contract was stripped from Connex last year.

RMT general secretary Bob Crow said: "It is astonishing that the government intends to privatise the franchise all over again, no matter how efficient public hands prove themselves to be."

The Strategic Rail Authority stripped French firm Connex of the service last June because of poor financial management.

Since then, the body has run the network through a wholly-owned subsidiary, South Eastern Trains.

Four companies - DSB (Danish State Railways), GNER Holdings Ltd, First Kent Integrated Railways Ltd and London South Eastern Railway Ltd - are in the running for the new franchise.