CANBERRA - The arrival of the biggest boatload of asylum seekers since the new wave of illegal migrants began building late last year has again set alarm bells ringing in Australia.

As the 194 people migrants were being taken into detention on Christmas Island in the Indian Ocean, reports emerged of as many as 10,000 more waiting in Malaysia for their chance to risk a journey that has claimed dozens of lives.

While the Opposition blames the relaxation of the harsh detention regime of the former Coalition Government for the resurgence of boat people, evidence is mounting that laws passed in Canberra have limited deterrent effect.

International agencies support Government contentions that the upsurge in illegal voyages since late last year are largely the product of wars, persecution and poverty, and reflect larger, similar, movements into other rich nations.

Further studies have shown that tough messages from Australia are often ignored, misunderstood or not received by people desperate to find safety and security in a new home, and that "shonky" migration agents encourage others.

But with amendments to immigration laws before Parliament and an Opposition desperate to erode the dominance of Prime Minister Kevin Rudd's Labor Government, the interception of the boat carrying Sri Lankan Tamils near Christmas Island has fanned political fires.

The interception was the 16th this year and has taken the number of asylum seekers held on Christmas Island to about 730, with more than 400 held in detention awaiting security screening and health checks.

So far, facilities on the island are coping. They can accommodate up to 1200 people, including the detention centre and community housing designed to ensure children - and their families where possible - are not interned behind barbed wire.

The Opposition claims that Rudd has not learned the lessons of history.

Australia progressively toughened immigration laws as successive waves of boat people arrived: Vietnamese escaping communist rule in the 1970s, Cambodians in the early 1980s, and the tsunami of the late 1990s that inflamed the 2001 federal election and led to a crackdown that choked the flow until late last year.

Rudd has maintained intensive patrolling by Navy ships, Air Force Orions and other agencies, and has retained mandatory detention for illegal migrants until cleared by security and health officials.

But he has ended indefinite detention, ensured children are not held behind bars, improved treatment, eased access to visas, and is ending rules that require asylum seekers to meet the cost of their detention.

The Opposition warns that Australia will pay as a result. Even as the latest boat approached Christmas Island, Malaysian authorities prevented a flotilla of small boats from reaching a larger vessel waiting with other asylum seekers to sail to Australia via Indonesia.

Yesterday Sydney Morning Herald correspondent Tim Allard reported from Kuala Lumpur that Malaysian and Indonesian police intelligence believe that between 7000 and 10,000 more people are preparing to make the journey.

Concern is also mounting that an influx of asylum seekers from Sri Lanka could conceal former Tamil Tigers fleeing after their defeat by government forces and potentially presenting a security threat for Australia.

Immigration Minister Chris Evans told ABC radio that despite combined efforts with Malaysia and Indonesia, and the dangers of a voyage that in recent months had claimed at least 20 lives, violence in Afghanistan, Pakistan and Sri Lanka would fuel a continuing exodus.

"We're absolutely determined to try and combat people smuggling," he said.

"But there's no end in sight in terms of the numbers of people moving through Southeast Asia, and we're going to have to keep up trying to meet the challenge, certainly over the next year or so."

Australia's recent defence white paper lists "potentially destabilising" mass migration flows as an emerging threat, and a report by the United Nations High Commissioner for Refugees said asylum claims increased by 28 per cent last year, with more than 15 million refugees worldwide.

The Government's rejection of Opposition claims that softer policies have led to a new flood of asylum seekers has been supported by Charles Sturt University researcher Dr Roslyn Richardson.

In the first study of asylum seekers' views of Canberra's deterrence messages, Richardson said many did not receive the warnings, and had little knowledge of Australian immigration policy - or even of the country.

The Migration Institute of Australia has also called for tougher regulation of agents after a study that said that while most registered agents performed to a high standard, migrants were exploited by "untrained, unregistered, unlawful, unscrupulous" agents both in Australia and overseas.