Colchester would consider a groundshare with rivals Ipswich next season if they win promotion to the Premiership.
Colchester should be in their new home by 2008
The U's Layer Road Stadium falls short of Premier League ground criteria and a planned new home is not expected to be ready until the 2008/09 season.
They can still make the Championship play-offs and are thinking about how they would approach the top flight.
Chief executive Marie Partner told BBC Sport: "Looking at the alternatives it would have to be Portman Road."
Colchester had hoped to move into their new ground at Cuckoo Farm this December but the Essex club is now not expected to take up residency until the 2008/09 season.
The latest developments concerning the new ground were not expected to be an issue as Layer Road has been fit to host the club for the last 70 years.
However, with promotion to the Premiership not out of the question, Layer Road could serve out its final days sooner than expected.
Partner added: "If it should happen and we get promoted there have to be serious discussions around the table because unfortunately Layer Road and its old facility does not fit Premiership criteria.
"We'd have to look at alternatives but we won't make noises about it until we look like we're moving back to the play-offs and it is a possibility.
"Obviously you put a contingency plan in place. It's something that's been loosely discussed a couple of months ago and would be something that Ipswich would have to think about - but commercially it's not ideal."
Layer Road in its current state boasts a capacity of 6,210, and, while it has been an intimidating place for visiting clubs to travel to this season, it is unsuitable for hosting the likes of Manchester United and Chelsea.
Partner explained: "One prime example of how the ground does not reach the criteria is the press facilities.
For directors that are used to style and comfort Layer Road has been a culture shock
"In the Premiership you have to make 150 spaces available on the half-way line. We went from six to 20 this season and had to lose some of our seats which belonged to season ticket holders and that was difficult enough.
"Other issues include dressing room dimensions and car-park sizes - we fall short in so many areas.
"We've managed to get away with it this season and that's been pretty tough because the clubs that have come down here have found it completely different. For directors and delegates that are used to style and comfort it's been a bit of a culture shock."
Partner admits that it is a lovely headache to have as the club enjoy life in the Championship after going up from League One the previous season.
She added: "We've thoroughly enjoyed this season. I've been here 20 years and there's a huge leap from League One to the Championship and an even bigger one to the Premiership.
"But we feel like we're in the Premiership at the moment, because we've known the hard and the bad times - but every time we succeed it makes you hungry to make that next stage."