A population many times higher than the current 6.9 million could be supported if money and technology were used to create the right environment, a United Nations consultant said. Professor Ronald Skeldon, a population expert formerly with the University of Hong Kong, said immigration from the mainland could help the SAR. He was asked by lawyers representing child migrants to provide evidence in their challenge to immigration laws. Professor Skeldon's statement will be considered with evidence from the Immigration Department, which warns of the dangers of encouraging an influx from the mainland. The professor said: 'As societies become more prosperous and more advanced technologically, the densities of populations which can be supported by these systems also rise. 'Hong Kong has emerged as one of the most prosperous cities in the world and, with vast amounts of capital to invest, should be able to construct the type of environment that will allow a population many times greater than at present to be supported at even higher standards of living.' Immigration in Hong Kong was not high compared to other big cities, Professor Skeldon said. He said the SAR had low fertility rates and immigration would prevent a decline in population. Claims that schools had been put under pressure by an influx of child migrants were 'somewhat short-sighted'. Professor Skeldon said the number of young people in Hong Kong had been declining. 'The immigration from China at present is really too small to make a significant impact on this declining trend, but at least it is adding to the demographic profile of Hong Kong through a supply of women and children.' He said the threat of illegal immigration was a 'red herring', with levels extremely low by historical standards. Geoffrey Ma SC, for the Government, told the Court of Appeal yesterday that allowing migrants to come to Hong Kong without complying with mainland restrictions would be dangerous. Mr Ma drew the court's attention to evidence provided by immigration officer Mak Kwai-yun. He said people wanting to assert their right of abode could resort to dangerous methods to get to Hong Kong that led to loss of life.