A review into why Kenilworth Station was opened late will not be published until next year because the group did not realise how 'complex' it would be to finish.
The station opened on Monday April 30 after several delays. It ended up costing £13.6 million.
Just before the station opened, Warwickshire County Council announced the creation of a 'Task and Finish Review' to look back at the key decisions made during the station's construction and work out what went wrong to learn lessons for future projects.
Organisations such as Network Rail, station operator West Midlands Trains, the Department for Transport, consultants SLC Rail, and Kenilworth Town Council are all taking part in the review.
The review was supposed to have been ready this autumn.
But it will not be published until next year because the group undertaking the review did not realise how difficult it would be.
A report from the group given to county councillors at an Overview and Scrutiny Committee on Friday November 14 stated: "The Kenilworth Station project was complicated and relied heavily on a number of partners working effectively together.
"A challenge for the Task and Finish Group has been to develop a sufficiently good understanding of these complexities to enable it to draw accurate conclusions and produce meaningful and effective recommendations."
Kenilworth town councillor Richard Dickson was frustrated at the delay.
He said: "This review was announced in April and was originally scheduled to have finished its review and reported back by this autumn.
"However, it is clear from the group’s latest report that its running behind this schedule because it has discovered that the station project and therefore a review of it was a far bigger exercise than envisaged.
"This is no surprise whatsoever to anyone who suffered as a result of the several delays in the train service starting."
And town councillor Richard Hales, who sat on the first meeting of the group this summer, felt the review was likely to be complicated at the time.
He said: “I just thought there was no way this was going to get done quickly. I think will be trying to unstand the role of Network Rail - they’re just so big.
“It’s very important that everyone’s held to account. If it takes longer, so be it.”
The Task and Finish Group is due to meet today (Monday December 3) for further discussion.
Warwickshire County Council has been approached for comment.