Police have recently been grabbing Pakistanis and other South Asians trying to sneak into Hong Kong from China. Some intelligence reports suggest a number of these illegal arrivals intend to head for Tsim Sha Tsui to swell the ranks of those seeking political asylum. Others are simply looking for jobs.

Whatever, we must continue our vigilance about people coming here illegally.

In 1979, Hong Kong was reeling under the twin influx of 1,000 Vietnamese arriving every day claiming refugee status and 1,000 mainlanders arriving daily seeking work or reunion with families.

The last Vietnamese were sent home in 1997. Over the past 20 years, the flood of arrivals from China has steadily declined. As China prospered, the need to swim the Shenzhen River to find work has been less compelling.

In 1986, police caught 20,539 illegal immigrants from the mainland. Almost all were swiftly sent back across the border. In 1992, 35,645 were returned and a further 37,517 in 1993. Numbers gradually started to drop as prosperity grew. By 2000 the number caught and sent back was just 8,476.

In 2003 the figure had dropped to 3,809. Last year there were only 2,191.

But now, just as we breathe a sigh of relief after many years and enormous efforts at combating illegal immigration from China, there is this new wave of undocumented workers coming from South Asia. They are arriving in nowhere near the numbers that in the past threatened to swamp us in a tidal wave of humanity. But it is still worrying.

How do they get here? It seems Pakistanis, Sri Lankans and Bangladeshis go on tourist visas to the mainland then find criminals prepared to smuggle them into Hong Kong. On payment of hefty fees, speedboats run them over Mirs Bay to landing spots along our east coast, where they are met by waiting taxis.

Who employs them? It's obvious just from looking at the faces digging up roads that more South Asians are employed as labourers. Presumably, those working in public view for major contractors have work permits and their papers are in order. But where do the others find work, given that anyone who employs them faces jail for three years and a HK$350,000 fine? Who's going to take the risk?

Plenty of people, believe it or not. Last year the Immigration Department arrested 12,468 illegal workers. One boss who foolishly hired a worker went to prison for 10 months. One migrant who unwisely took a job was locked up for 15 months. Harsh? Yes. Necessary? Absolutely.

Legislative Council member Raymond Ho Chung-tai, who represents the engineering functional constituency, points out there is no war or civil disorder in Pakistan or Bangladesh causing people to flee their homeland.

'We have to be fair to everyone and at the same time protect the interests of Hong Kong,' he said.

Lui Ming-wah, who represents the industrial functional constituency, says bluntly that under our immigration laws, if people enter illegally we should send them back to wherever they came from.

'We should not give them asylum,' he said. 'They should be returned. There is no real oppression in those countries.'

I agree. For two decades we were cynically used as a dumping ground for Vietnamese refugees. Even when it became obvious arrivals were not ethnic Chinese fleeing racial persecution or southerners trying to escape vengeance for the war, we were badgered into accepting North Vietnamese who were economic migrants.

Now we are once again coming under siege. Africans, South Asians and unfortunates from elsewhere are arriving as tourists then claiming refugee status. Pakistanis and Bangladeshis are being smuggled in to find work.

No matter how sympathetic we may be to their plight, we've got to realise that Hong Kong cannot play host to everyone who wants to come here, for whatever reason. After consideration of their individual plight and guarantees that they will come to no physical harm, all those who enter Hong Kong illegally should be sent back from where they came.