UPDATE: A British evacuee from the Explorer tells her story.
UPDATE 20.25: Pictures of the stricken ship sinking.
UPDATE Saturday 24 November 20.14: The BBC reports that a Chilean military plane is on its way to King George Island where the 154 tourists and crew spent last the night.
UPDATE 13.29pm: Here are some camcorder stills taken from Hurtigruten's MS Nordnorge, which is involved in the rescue. These are being updated.
UPDATE 12.44pm: Here is the map of the location.
View Larger Map
UPDATE 12.40pm: The Sun newspaper has published this picture of the ship.

UPDATE 12.28pm: Gap Adventures has released an emergency number for relatives - 00 1 800 465 5600 ext 101.
UPDATE 12.27pm: Lloyd’s List reports that the Explorer had five deficiencies at its last inspection, including missing search and rescue plans and lifeboat maintenance problems.
UPDATE 12.22pm: Gap Adventures have confirmed that 24 british nationals were on board.
UPDATE: 11.55am: The Maritime and Coastguard Agency has said that 152 people on board Explorer have now been rescued by Endeavour. Hurtigruten's MS Nordnorge has arrived to collect passengers. MCA said the Rescue Coordination Centre in Falmouth is helping out with the rescue's communication.
UPDATE: 11.50am; Travel Weekly has now put a link to a video of Explorer on the website.
Click here to see it.
UPDATE: 11.11am; Sky News is reporting that MS NordNorge and Endeavour have arrived at the scene.
UPDATE: 11.08am; Hurtigruten has just advised Travel Weekly that its ship MS Nordnorge has arrived in Antarctica and will reach the Explorer at around 11.30am Norwegian time.
UPDATE: 11.01am: The British Antarctic Survey press team is having a tea break - we will keep on trying them for a comment on the environmental immpact.
UPDATE: 10.58am: There are concerns about the impact on the environment of the Explorer sinking.
UPDATE 10.53am: The Explorer is not owned by Noble Caledonia, as has been reported in the press.
UPDATE 10.49am: BBC confirms Britons, Canadians and Americans were on board. There is no emergency number as yet.
UPDATE 10.47am: Gap adventures PR confirms all passsengers are safe and that there are staff on board trying to stabilise the ship.
UPDATE 10.40am: Sarah Longbottom is telling ITN that the Explorer is fitted to ice standards and that GAP Adventures is a member of the International Association of Antarctic Tour Operators. Sarah points out that the IAATO issues safety guidelines but there are no legal requirements to adhere to these. She goes on to say that this incident will knock consumer confidence in cruising.
UPDATE 10.34am: Travel Weekly reports, Hurtigruten MS Nordnorge is to be first ship to sinking Explorer.
UPDATE: 10.31am: Travel Weekly editor talking to ITN
UPDATE 10.26am: According to Lloyd's List the Explorer is registered to Gap Shipping.
UPDATE 10.09am: Royal Caribbean has been inundated with calls from people concerned its ship, Explorer of the Seas, is the one involved.
UPDATE 9.58am: GAP Adventures have confirmed that they are currently chartering the ship.
UPDATE: Travel Weekly has just spoken to Andy Harmer at ACE and told us that he belives the ship is currently chartered by GAP Adventures.
UPDATE 9.55am: We are currently trying to establish who has chartered the ship for this trip.Unconfirmed reports are that it is a UK company.
Sky News reports there is a major rescue operation underway after a cruiseliner hit an object and began sinking in the Antarctic Ocean. More than 150 people on board are being evacuated and moved to life rafts and a nearby ship off the Argentinian coast.
The ship is the MV Explorer, which is used by companies such as GAP Adventures.
Here is a picture of the ship on the GAP Adventures site.

More updates on Travel Weekly's website.
Martin Couzins, online editor