The number of peak-hour trains on the Connex South Central network which arrived late was higher than the same time last year, as the under-fire rail firm gave another dismal showing in performance tables.

And Connex's poor time-keeping could have serious consequences in its fight with rivals GoVia to keep the South Central franchise.

Rail bosses have warned that the poor figures will be taken into consideration when the decision on who gets the franchise is made in the autumn.

The chief executive of the Strategic Rail Authority, Mike Grant, said: "These results are not satisfactory. Some of it can be attributed to events outside the control of the train operating companies.

"Operators need to pay attention to the immediate problems under their control. It will influence our decision on franchise replacement."

In the period between the end of April and the end of July this year just 86 per cent of Connex South Central peak-hour trains reached their destination on time.

Over the same period last year nearly 93 per cent of their trains arrived when they were supposed to - the seven per cent drop was the worst in the country.

And in the all-day performance figures Connex South Central fared little better, with just under 87 per cent of trains on time, a five per cent drop from last year.

Rival firm Thameslink, which owns GoVia, managed a slight improvement with its punctuality but still had 14 per cent of its rush-hour trains arriving late.

Connex said the delays were due to overcrowding on trains which resulted in larger numbers of people getting on and off at stations, holding up trains.

The trains are overcrowded because Connex has been forced to cancel numerous services due to a chronic shortage of drivers.