A plan to ease the one-piece cabin baggage restriction for airline passengers in January could lead to mass confusion, airport officials say.
The Department for Transport has said more than one piece will be allowed after 7 January, provided airports have purchased improved security scanners.
Yet airport operators say it is also up to airlines to decide if they want more cabin baggage on board flights.
And the cost of the new 3D scanners means small airports will not buy them.
Neil Pakey, the head of the Airport Operators' Association and the managing director of Liverpool's John Lennon airport, predicts widespread passenger confusion as different rules are implemented at airports around the country.
"For us, an airport like Liverpool just would not have anything in place by 7 January," he said, adding that there is only one UK supplier of the new three-dimensional scanners required by the Department for Transport and the machines cost "hundreds of thousands of pounds" each.
"Some of the operators say there's going to be a great deal of confusion because it looks as if there may be different rules at different airports," he said of the gradual easing of the bag limit.
Mr Pakey said the push for an increase in cabin baggage is coming from large airlines, such as British Airways, in order to accommodate their passengers using London airports.
He said that even if some airports allow more than one piece of luggage, the airline might stick with a one item limit, furthering the confusion.
"It will be very inconsistent and to be honest, it's not an easy situation," he said, adding that he feels Transport Minister Ruth Kelly is doing the best she can to accommodate passengers amid a real security threat.
He said that after 7 January the flying public needed to find out what each airline permits at each airport, not just whether or not the airport they are departing has approval to scan more than one bag.
A spokeswoman for BAA, which runs seven UK airports including Heathrow, Gatwick, Stansted and Glasgow, says it does not yet know whether its added security equipment is sufficient to satisfy the government in time to make changes on 7 January.
"The DfT make the final decision on which airports are allowed to implement [the increased cabin baggage]," she said.
A DfT spokeswoman said the easing of restrictions will be a gradual process and passengers must keep themselves informed of any changes.
"It is for airports and airlines to ensure that their customers are kept informed about the number of cabin bags they may carry and the continuing restrictions on liquids," she said, adding that restrictions on size of bags and liquids will not change.
The DfT says new 3D scanners are not an absolute requirement for airports looking to increase the amount of cabin baggage allowed.
"Investment in new technology is not the only way an airport can increase capacity - they could also do so through additional levels of staff for example," the spokeswoman said.
The dimensions of hand luggage must not exceed 56cm x 45cm x 25cm (22in x 17.7in x 9.8in approx), including wheels, handles and side pockets. This is equivalent to the size of a small roller suitcase.