text: Some 563 were held or arrested by Port of Dover police officers last year - up from 148 in 2013, a BBC Radio Kent Freedom of Information request shows.
  The figures come days after dozens of migrants attempted to storm the Channel Tunnel's Calais terminal.
  The Home Office said it was providing funding to bolster security and that many crossing attempts had been foiled.
  The FoI shows 46 illegal immigrants were detained or arrested at Dover - one of the main gateways to Britain - between January and April this year.
  The number of detentions and arrests is also up significantly from 2012, when 105 were held or arrested.
  Around 3,000 migrants from countries including Eritrea, Syria and Afghanistan are camped at a site dubbed "the Jungle II" near the Port of Calais.
  French aid workers have reported a "catastrophic" situation there.
  Road Haulage Association chief executive Richard Burnett, who recently visited Calais, said migrants are going to great lengths to cross the Channel.
  He told Radio Kent: "They think it's a great place to be and (Britain's) their target. They will do anything they possibly can to get into the UK."
  Last week, Channel Tunnel services were delayed and cancelled after immigrants entered restricted areas on the French side.
  And last month hundreds of migrants tried to board UK-bound lorries amid chaos as a strike forced the suspension of services through the tunnel.
  Eurotunnel said at the time that the number of migrants in the Calais area was the "highest ever".
  Hauliers have been advised by the Freight Transport Association not to stop within about 60 miles (97km) of Calais, to stick with other drivers and make sure padlocks are always kept on vehicles.
  Responding to the latest figures, a Home Office spokesman said 40,000 attempted illegal crossings of the Channel had been foiled last year.
  He added: "We are providing funding to bolster the security of ports in northern France and Belgium, including a Â£2m upgrade of detection technology, a Â£1m extension of dog searching capacity and Â£12m to reinforce security at Calais and other ports.
  "During the current period of disruption to cross-Channel services, Border Force has put its contingency plans into operation to ensure security is maintained.
  "We have deployed additional Border Force staff and sniffer dogs in northern France as well as bolstering screening checks at Dover for both tourist and freight vehicles."
  The Port of Dover Police is a non-Home Office constabulary funded entirely by the port authority, Dover Harbour Board.
  Port of Dover Police is not responsible for border security, which is down to the Border Agency and Kent Police frontier operations.
target: There has been a large increase in the number of illegal immigrants detained or arrested by police at Dover.