In the last quarter that former franchise holder Thameslink operated the service - January to March 2006 - there were 33 complaints per 100,000 passenger journeys.

In the first quarter after FCC took over - April to June - the level of complaints went up to 88 per 100,000 passenger journeys.

But after FCC introduced new restrictions on the use of cheap day return tickets during the evening peak, the number of complaints almost tripled to 254 per 100,000 passenger journeys.

The figures are revealed in the latest National Rail Trends published by the Office of Rail Regulation.

Association of Public Transport Users spokesperson Adrian Jackson-Robins, who lives in Harpenden and commutes to London, said: "The restrictions might have made commercial sense for the company but it was a public relations disaster that motivated a vociferous body of people to complain."

He added: "There have been a series of disastrous days on the line which have also generated a large number of complaints, but in fairness to FCC most of these problems have not been of their making. They have been down to Network Rail."

Disappointed

FCC's train punctuality reached almost 89 per cent compared to 84 per cent for Thameslink in its last quarter.

An FCC spokesperson said: "We are disappointed that the number of complaints has increased. We take all complaints and customer feedback very seriously and since taking over the franchise in April, we have invested heavily in our communications with customers.

"We work hard to continually improve our service. We have made a number of improvements this year, but we do recognise there is more to do.