On its website, Telegraph said the Mekong cruises offer a window on time-honoured traditions and contrasting Far Eastern cultures.

The Mekong River has been of vital cultural, political and ecological significance to Southeast Asia for centuries. Rising in the Tibetan plateaus of China's Yunnan province, it negotiates the dense rainforest, open plains and rice fields, fishing villages and floating markets, ancient temples and shrines of Vietnam and Cambodia.

The cost for an eight-day river cruise from Siem Reap in Cambodia to Ho Chi Minh City in Vietnam is around £1,436 per person excluding flights, departing in June 2015.

Rounding out the top five list are Ganges channel (India), Yangtze (China), Irrawaddy (Myanmar), and a tour from Delhi to Kolkata (India).