Cotswold Line passengers' support for plans to reinstate double track on much of the Oxford-Worcester route has made a big impression on a key railway official.

Chris Bolt, the chairman of the Office of Rail Regulation, who will decide next month whether to approve funding for the scheme, has been flooded with messages calling for a favourable decision, the annual meeting of the Cotswold Line Promotion Group heard.

Mark Hopwood, the performance director of train operator First Great Western, told members of the passenger group that Mr Bolt had told him he had never seen so much lobbying in favour of a project. Mr Bolt became ORR chairman in 2004.

"The ORR has clearly got the message," said Mr Hopwood at Saturday's meeting in Moreton-in-Marsh, Gloucestershire.

Network Rail revealed last month that it was seeking the ORR's consent to put back double track on 20 miles of the line, including the section from Charlbury to Ascott-under-Wychwood, to cut delays and improve reliability. The work could cost more than £50m.

Lord Faulkner, the CLPG's president, and its chairman Derek Potter urged all those present to keep up the pressure on the ORR and the Department for Transport in the remaining weeks before Mr Bolt decides whether to approve Network Rail's Strategic Business Plan for 2009-14, which includes the Cotswold Line enhancement scheme.

Mr Hopwood said FGW had been working closely with Network Rail on the project and added: "We very much hope that the plan for the Cotswold Line is delivered."

He said punctuality on FGW's network had improved markedly since the turn of the year, with 90.59 per cent of all its services on time last month.

The figure for the Cotswold Line had climbed to 85 per cent, from just 64 per cent in January, when it was the worst performing route on FGW's network.