Unexploded bombs, seagulls and entrances too narrow for lorries forced the Department for Transport to discount all but one of the options for Operation Stack emergency lorry parks, it has emerged.

Documents released under the Freedom of Information Act reveal seven sites were shortlisted as possible temporary alternatives for when Operation Stack was in force but only one - Manston Airport - was considered acceptable.

The six rejected were Ebbsfleet International Station; the Sir John Moore Barracks, Folkestone; Lodge Hill Training Centre at Chattenden, Medway; The Port of Ramsgate; Kenley Aerodrome, Surrey and the former Howe Barracks, Canterbury.

The attempt to find an alternative to parking HGVs along stretches of the M20 was triggered by the longest continuous spell of Operation Stack last summer, when for 32 days it was in force and gridlocked much of the county.

But the quest for alternative solutions - ordered by PM David Cameron - proved frustrating for the government. Several were only capable of holding 100 to 150 lorries when space was needed for 3,000.

Ebbsfleet Station - which was publicly identified by ministers as an option before the review - was ruled out partly because entrances to the site were not wide enough.

According to a report by Ministry of Defence officials, which weighed up the pros and cons of each site, Ebbsfleet was dismissed because while it had capacity for 400 HGVs “unfortunately, the entrance to the car park is only suitable for cars and is too narrow for HGVs.”

Widening the entrances at Ebbsfleet would be a “significant task and would require contractor assistance to remove the electric barriers carefully so they could be reinstated at the end of the operation,” it added.

It also said that the ability to control traffic in and out during Operation Stack was poor and a “significant upgrade” would be required.

The risk of unexploded bombs led to the rejection of two other options: Lodge Hill Camp, at Chattenden and The Port of Ramsgate in Thanet.

In the case of the Port of Ramsgate, the DfT report concluded it was a viable option with space for 250 and 300 HGVs but both poor access and “a reported UXO [Unexploded Ordnance]” presented too much of a risk.

It also cited as a concern the presence of seagulls, saying they “may be attracted to food/waste and cause a nuisance to the local population.”

Lodge Hill, a former munitions factory in Medway was ruled out because it would take too long to clear the site of what the report describes as “recently discovered” unexploded bombs.

Officials also highlighted the popularity of the area among anglers, suggesting they could present a security risk and one option might be to “consider suspending fishing permits” until Operation Stack was over.

Sir John Moore Barracks, Sandgate, where the Royal Gurkha Rifles are based, was ruled out for a host of reasons. These included poor access and constrained space for manouevring HGVs on and off the site.

Manston Airport emerged as a clear favourite, with the DfT report saying “the site infrastructure would require little enhancement”.

It cautioned that “entry and exit points may have to be carefully selected to accommodate local population/authority concerns about potential traffic issues.”

The 800 acre site was not supported by Kent Police, which raised several concerns about the site. South Thanet MP Craig Mackinlay said it was a crackpot idea while colleague Sir Roger Gale labelled it insane.

However, the site has yet to be tested as since the summer disruption, Operation Stack has not been implemented.

The government announced last year it was allocating £250m to find a more permanent solution to Operation Stack and is consulting on two options for a holding area on sites off the M20 at Folkestone.