Airport-style security scanners are to be used at London's Paddington railway station, the government is to announce.
It is thought checks would be trialled on the Heathrow Express
Heathrow Express passengers will walk through the X-ray machines as part of a trial to establish whether tighter security is possible on the railways.
But extending the checks across England would mean redesigning stations and could create more congestion.
It follows bomb blasts on London's transport network on 7 July which killed 52 people and injured 700.
There are no stops on the Heathrow Express between Paddington in west London and the airport, so tighter security is easier to administer.
But it is thought the process of redesigning stations to create secure areas combined with inevitable queues formed by people waiting to go through X-ray machines would be expensive and cause more delays.
The BBC correspondent Tom Symonds said ministers would want to avoid more pressure on the already-overcrowded railways.
And Hassard Stacpoole, from the Association of Train Operating Companies (Atoc), told BBC News: "The railway system operates as an open-access sort of system.
"I think the reality is that it would be an impractical suggestion to have airport scanners at every single station around the country."
Baggage checks are common at airports, where passengers have to turn up hours before they are due to fly.
But Transport for London (TfL) has pointed out that while Heathrow handles 67.1 million passengers a year, the Tube - where three of the 7 July bombs exploded - carries 976 million.
Brian Cooke, chairman of London Travelwatch, said there was no system available that could cope with the volume of Tube passengers.
He said everyone wanted maximum security but there were concerns the checks would mean more delays and congestion.