A leading Indian activist at the World Urban Forum in Vancouver has lashed out at such conferences, saying they do little to better the lives of the poor.
Organisers say the summit is a chance to exchange of ideas
Former slum-dweller Jockin Arputham criticised the forum's location and delegates who he said were more keen on writing reports than ending poverty.
Thousands of experts, politicians and activists are meeting to discuss the world's growing urban problems.
Organisers say the forum is a way of exchanging ideas and raising awareness.
Time and money
"We are very, very critical about this kind of conference," said Mr Arputham, president of India's National Slum Dwellers Federation.
"The amount of time and money spent on this World Urban Forum - how many consultants have been employed for carrying out this kind of conference?"
He said international gatherings like the Vancouver meeting should be held in cities like Mumbai or Cairo, among the urban poor whose problems are being debated.
Mr Arputham also criticised the United Nations for failing to stop forced evictions of poor city dwellers by private developers and government-sponsored aid programmes.
"Where is the teeth of the United Nations?", he asked.
'Chance to connect'
The BBC's Daniel Lak at the conference said delegates applauded Mr Arputham's critical speech at a debate on slum policy, but many also say they are picking up new ideas from colleagues from other countries.
He says conference organisers admit that they are open to accusations of staging a talking shop with no new spending commitments or new programmes to help the poor.
Vancouver's mix of skyscrapers, sea and forests is widely admired
But Anna Tibaijuka, head of the UN settlements agency UN Habitat, which is sponsoring the forum, defended the gathering:
"A forum like this provides a chance for people to know, to connect with the rest of the world, to know that people care.
"We raise awareness, and once we raise awareness, then we increase the chance for having concerted action."
The 2006 forum is the third meeting of its kind. Its western Canadian host city is widely lauded for its high quality of life.
On the agenda are the simultaneous challenges of tackling urban poverty, protecting the environment and creating healthy, pleasant cities as the world's urban population soars.
A UN report released ahead of the summit estimated that more than half of the human race would live in urban areas by the end of 2007.
By 2030, 80% of people would live in cities, it predicted.
An estimated one third of city dwellers globally live in slums, with the problem worst in sub-Saharan Africa, where slum-dwellers make up more than 70% of the urban population.