A senior industry source says GNER, Thameslink, Silverlink and South West Trains are likely to get favourable treatment by the Government. All have franchises expiring in 2003 or 2004.
He said GNER, the Sea Containers subsidiary that runs high-speed trains to Scotland, and Thameslink, which runs from Bedford to Brighton, were the most likely candidates.
But another industry figure doubted that John Prescott, the Deputy Prime Minister with responsibility for railways, would reward so many southern England operators.
Silverlink, part of National Express, is handicapped by the latest official performance figures that rated it the country's worst operator. It was the only operator to get an E grade owing to unreliable trains on one of its lines.
South West Trains, owned by Stagecoach, was reprimanded in the early days of privatisation for sacking too many drivers and having to cancel trains. But it is one of few operators making major additions to this summer's timetable.
Successful bidders will have to offer major investment. GNER, which has attracted 18 per cent more passengers since it took over the line, said it would buy up to 10 new tilting trains to ease overcrowding.
Thameslink, which runs the most overcrowded trains in the UK, has come up with plans to cope with the problems that will be caused when Railtrack starts its pounds 800m upgrade.
One operator said: "The sooner the [franchise] decision is made, the sooner the industry can concentrate on delivering the improvements."
Only a limited number of franchises will be renewed, and rail operators have been told that they must compete with each other for the right to be part of the first wave of renewals.