The team behind the £1.4 billion construction project have consistently claimed that it is on course to be completed in time to open to traffic in December as scheduled.

However, reports in The Scotsman suggest that the bridge is in fact running months behind schedule and will not be finished until well into 2017.

It quotes a staff source saying: “Everyone agrees there is no chance of it finishing by the end of the year. It could be months late - maybe even the middle of next year.”

It is understood the delay is due to the time it is taking to finish work on the bridge’s road deck, with poor weather over recent months being blamed for the slow-down.

Transport Scotland did not dispute the delays but said that the construction team was trying hard to meet the timetable.

A spokesman said: “Forth Crossing Bridge Constructors is making every effort to open the bridge as soon as possible, despite the challenge that the weather presents.”

The Forth Crossing Bridge Constructors (FCBC) consortium comprises Hochtief, Dragados, American Bridge and Morrison Construction.

The construction site shut down for several days in April following the death of John Cousins, 60, who was struck by the boom of a crane.

A project milestone was reached last month as the roadway linked to the north shore for the first time.

The final segment of deck was put in place which means that now the bridge’s north tower is joined with the north approach viaduct into Fife.