Councillors at Buckinghamshire County Council’s Development Control Committee voted in favour of a deferral due to legal grounds.
A legal adviser told the hearing that since the consultation into the action is due to finish in two weeks any other decision than a deferral could result in costly legal action.
Tesco had amended its application to apply for an extra year for the building materials to be brought in after the original permission ran out last year.
The decision has been deferred twice, in September and November of last year, because approval from Network Rail was not in place.
Tesco wants to use the railway and conveyor system to bring the bulk filling materials to the site. It says it would be more environmentally friendly and also more pleasant for locals, who otherwise would have to see more than 10,000 lorries pass through the town.