According to the British team, the Hang Son Doong is larger than the Deer Cave in Sarawak, Malaysia, which at more than 100 yards high and 90 yards wide is currently recognised as the world's largest cave passage.
"It is a truly amazing sized cave and one of the most significant discoveries by a British caving team. The complete survey is at present being drawn up but initial estimates show the main passage to be 200 metres (656 ft) high in places and possibly greater in some sections.
"Much of the passage width is over 100 metres (328 ft) but certain sections are over 150 metres wide (492 ft)," 'The Daily Telegraph' quoted Adam Spillane, a member of the 13-man expedition, as saying.
The British team, which has discovered the cave in mid-April with help from representatives of the Hanoi University of Science, is now in the UK to analyse its findings.
The team spent six hours trekking through the jungle to reach the cave. Climbing down into a large chamber, they had to negotiate two rivers before reaching the main passage of the Hang Son Doong.
Spillane said that the entrance to the cave was first found by a local man, Ho Khanh, in 1991.
"Khanh has been a guide for the team in many expeditions to jungle to explore caves and this year he took a team to the cave which had never been entered before by anyone including local jungle men.
"This was because the entrance which is small by Vietnamese cave standards and emitted a frightful wind and noise which was due to a large underground river," he said.