Holidaymakers are being warned they face lengthy delays at European airports this summer after border checks were tightened.Passengers have been forced to wait in queues for up to four hours – longer than some of their flights – after arriving at airports popular with British tourists.The delays are reportedly being caused by the introduction of newly-toughened and more time consuming immigration checks.The problem – at what is traditionally already the busiest time of the year for flights – is being made worse by a lack of border officials on the continent, it is claimed.An association representing airlines said queues stretching for “hundreds of metres” are in some cases causing passengers to miss their flights.It warned that “shameful” queues can be expected at airports including Madrid, Palma, Lisbon, Lyons, Paris Orly, Milan and Brussels. Some flight delays have increased by 300 per cent in a year, it claimed. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. Airlines for Europe (A4E), the association that represents carriers such as British Airways, Ryanair and easyJet, said lengthy delays had been caused by many countries failing to provide enough staff for passport checks.Thomas Reynaert, A4E’s managing director, said: “Travellers face long lines and can’t get on their flights. Queuing for up to four hours has been the top record these days. Queues form at Barcelona airport ahead of security checksCredit:Manu Fernandez/AP Amsterdam airport @Schiphol is a disaster again today. Schengen-passport control queue extends beyond E-gates 4hrs waiting time #noholiday pic.twitter.com/X75Q8ziML2— Joepie (@joep19711) June 27, 2017 The problem is being blamed on the introduction of tighter European Union-introduced border controls in Schengen, the border-free area that incorporates most EU member states.Previously, British travellers have been given only visual passport checks by European border officials.But new rules, which were introduced after a series of terror attacks in Europe, mean checks against a series of databases are now carried out on each passenger from non-Schengen countries.The new tests, on both entry and exit, are said to take around two minutes per passenger. @SimonCalder queues for passport control at Palma airport this morning – what a farce! pic.twitter.com/cIunShy9r6— Catherine Little (@calittle1967) July 29, 2017 “Airports like Madrid, Palma de Mallorca, Lisbon, Lyon, Paris-Orly, Milan or Brussels are producing shameful pictures of devastated passengers in front of immigration booths, in lines stretching hundreds of metres.”At some airports, flight delays have increased by 300 per cent compared to last year.”A4E warned that the situation could worsen in the coming weeks as the new regulations have not yet been fully implemented. The six-month period to put the enhanced checks in place ends on October 7. EU member states have until the autumn to implement enhanced border checks, but many have already introduced them.A spokeswoman for the Association of British Travel Agents said: “New, stricter passport checks are resulting in longer queues at some airports, including Palma, which is already busy due to a significant increase in passenger numbers.”Tour operators will ensure that customers get to the airport in plenty of time so that they are not in danger of missing their flights.”However, independent travellers will need to check the situation with their airlines and, where necessary, ensure they factor these longer queuing times into their travel plans when flying in and out of the airport.”It is also extremely important that border control check points are sufficiently resourced so that queuing times are kept to a minimum.” The Government has been urged to use “whatever influence it can” to pressure EU states to adequately staff their airports.Airlines UK, an industry body representing UK-registered carriers, said it had warned the Department for Transport (DfT) about the problem in May, although they were told by ministers the issue had eased. Have you been hit by long airport delays in Europe? Let us know your experience by leaving a comment below. Tim Alderslade, the body’s chief executive, said: “Clearly the situation has changed markedly as we enter peak holiday season, and it is now up to the UK Government to work with industry to use whatever influence it can within the EU to persuade Schengen Member States to resource their border operations properly.”Pictures on social media in recent days have shown long lines of passengers in crowded terminals.