The government was told it would be "lunacy" to privatise Britain's only publicly owned train operator after official figures showed South Eastern Trains was one of the best performers in the network.

The punctuality of the franchise rose from 78 per cent to 83.4 per cent in the three months to September.

South Eastern Trains has been in public hands since the Strategic Rail Authority sacked the commuter service's French operator, Connex, a year ago for poor financial management.