Airports have criticised the government’s sudden re-introduction of 100ml limits on liquids in hand luggage last weekend.

The Airport Operators Association (AOA) said it had left airports “frustrated” and created uncertainty and confusion for passengers as the busiest time of year approached.

After installing high-tech new scanning equipment, some regional airports had scrapped liquid restrictions. Major hubs had not yet fully switched to the new rules, but are rolling out the machines.

The transport secretary has insisted the re-imposition of the old limits is “temporary’” but it’s unclear how long the situation will last.

The government requires all UK airports to upgrade to “next generation” security.

New scanners which produce 3D images should mean liquids up to two litres and laptops can be kept in hand luggage to go through security.

The likes of Heathrow, Gatwick and Manchester were allowed to miss the latest deadline for installing them – 1 June this year – after various logistical challenges.

However London City, Teesside, Newcastle, Leeds-Bradford, Aberdeen and Southend had complied on time and dropped the old liquids rules – some as early as Spring last year.

Birmingham completed its installation but was told to keep the 100ml limit while waiting for regulatory approval.

But on Friday, an unexpected announcement from the Department for Transport (DFT) said that from Sunday, liquids, gels and pastes could once again only be taken through airport security in containers of 100ml or less.

The DFT said it was not in response to a specific threat, but “to enable further improvements to be made to the new checkpoint systems”.

The sudden change caused consternation among airport bosses, who were only informed on the Friday.

Karen Dee, chief executive of trade body the Airport Operators Association, said hundreds of millions of pounds were being spent on a “huge” programme of change, as instructed by the government.

She said airports supported decisions on security, but Friday’s “surprise” announcement “was sprung on us with very little time to react”, and this “created uncertainty for passengers just as airports enter their busiest periods of the year”.

“It has also put airport operators in a challenging position, with very limited time to prepare for the additional staffing and wider resources that this will require, and no clear idea of when this issue will be resolved.”

Airports who had fully switched the new systems and have trained and rostered their staff accordingly, are most affected, unable to use the expensive, new equipment to its full potential.

The change is understood to have led to more items being rejected or confiscated as passengers have turned up expecting to be allowed to take larger containers through.

Some larger airports who were only part way through their roll-outs had been using the new scanners in some areas so have also had to quickly alter ways of working.

Thirty airport bosses, along with the AOA, have jointly written to the transport secretary, aviation minister and civil servants today in response to Friday’s announcement.

Among the questions they want answering are how the decision was taken, what it means for airports who are part-way through their roll-out – with implications for staff training programmes – and how long the reversion to the 100ml limit will last.

Ms Dee said airports were doing all they could to mitigate the impact. She asked passengers to come prepared to comply with the liquid limit until advised otherwise.

The DFT has been approached for comment.