The median salary of Hong Kong's top earners is HK$88,800 a month, 26.1 times the poorest 10 per cent, government figures show.
Overall, one in six people, or 17.6 per cent of 6.7 million people, struggled with poverty in the second quarter of this year, up 0.6 percentage points from last year, Oxfam Hong Kong said.
The figures, retrieved by the group from the Census and Statistics Department, show that the median household income of the lowest-income group was HK$3,400 a month. That was an increase of HK$400 in the last nine years, during which time the city's richest 10 per cent saw their median monthly income surge by HK$18,800.
In 2003, the top 10 per cent of the city's households made HK$70,000 a month - 23.3 times the lowest-paid group.
"The income gap between the rich and the poor has been increasing over the years. The number of poor people in Hong Kong has also been steady and slightly growing," said Oxfam director general Stephen Fisher. A 10-year high of 194,100 households with at least one family member working were considered poor - living on less than half the median income for city households of corresponding size. On that basis, someone who earns less than HK$3,600, or HK$8,000 for a two-member family, is considered poor.
The poverty rate among working households was 10 per cent - the second-highest rate since 2008, and the same as in 2003 and 2009.
This category covers people who are doing a full-time job, yet still make an income that leaves them unable to take care of their families, Fisher said. "I think this is a serious problem."
Between 60 and 70 per cent of working-poor households consisted of three or four family members, said Wong Shek-hung, acting Hong Kong programme manager for Oxfam, citing statistics since 2003.
She added that while 113,500 working-poor households had a monthly income lower than Comprehensive Social Security Assistance could offer, only 9.8 per cent of them, or 11,067 households, lived on CSSA.
Wong attributed this reluctance among the poor to seek the assistance to a "negative perception of CSSA recipients", which tarred those who relied on aid as lazy.
Fisher, who is on the government-appointed Commission on Poverty, said he would urge authorities to introduce a low-income family allowance for the working poor who earned less than CSSA payments but were loath to apply for assistance.
He also advocated an annual review of the minimum wage level. It is now reviewed at least once every two years.
Meanwhile, government figures released in June showed that the city's Gini coefficient - a scale from 0 to 1 on which higher scores indicate greater income inequality - reached a record high of 0.537 last year.