The All Weather Lifeboat took to the water shortly after 11:25 and is currently searching off the Bembridge coast in the busy cross-Channel ferry lanes.
Coastguard Rescue 104 helicopter from Lee-on-Solent is also on scene conducting an aerial search.
Island Echo understands the woman is a missing ferry passenger from the Brittany Ferries owned ‘Mont St Michel’.
UPDATE @ 12:58 – Brittany Ferries have confirmed to Island Echo this lunchtime that they are working with HM Coastguard after raising an alarm that a passenger may be missing from their vessel Mont St Michel.
A spokesperson has this afternoon said:
“When our overnight sailing from Portsmouth to Caen (operated by our ship Mont St Michel) docked at its destination this morning, an unattended bag, passport and other personal effects were discovered in a cabin, suggesting that a passenger may be missing.
“The alert was raised and we are now co-operating with HM Coastguard who are co-ordinating a search in the English Channel”.
It is understood the missing woman was last seen at 23:53 last night and is feared to have gone overboard during the cross to France.
A wide-scale search is now taking place, with the Mont St Michel approaching Portsmouth on its return leg from Caen.
UPDATE @ 16:02 – The search for the missing passenger has been called off in the last few minutes after more than 4 hours of searching, according to the MCA.
Bembridge RNLI lifeboat and Coastguard Rescue Helicopter 104 have both been stood down and have returned to station.
The search is not set to resume unless further information is received.