A project to enable part-time workers to buy flexible rail season tickets was delayed and ran millions of pounds over budget, according to a spending watchdog.

Eleven operators running trains into London were expected to offer discounted travel for such passengers by 2014 but only one, c2c, has achieved this, the National Audit Office (NAO) said.

Its report stated the Department for Transport (DfT) established the scheme in January 2012 with a £45 million budget, but £54 million was spent.

The South East Flexible Ticketing (Seft) programme was created to accelerate the introduction of smart cards on the rail network in a bid to enhance the experience for passengers and reduce the cost of selling tickets.

But passengers on just five train companies operating services in south-east England can now buy season tickets using the technology, the NAO investigation found.

A 2014 business case stated that achieving the economic benefits of smart ticketing depended on a take-up of 95% for season ticket sales, but DfT figures for participating rail firms show just 8% was achieved in the 12 months to March.

The project was paused three times and reset twice, with its scope reduced and budget revised each time.

Plans to enable passengers to pay for travel using contactless credit and debit cards - as is widespread across the capital - were abandoned in December 2014 following significant cost increases.

In total, the Government has spent at least £120 million to achieve the current level of smart and flexible ticketing in the South East, the NAO said.

The Seft programme was closed by the DfT this month following a ministerial decision that the rail industry should take the lead on smart ticketing.

A DfT spokesman said: "This was an ambitious programme to lay the foundations for smart ticketing for rail passengers across the country.

"It introduced smart card season tickets on five train operators, upgraded over 450 stations and created a hub for smart ticketing to be introduced across the entire rail network.

"The Seft programme means more than 400,000 season ticket holders now have access to paperless season tickets.

"Smart ticketing remains a priority for the Government and we continue to work with the RDG (Rail Delivery Group) and train operators on its roll out across the country."