His laudatory assessment of the nation's human rights progress since the end of its civil war was in stark contrast to that of British Prime Minister David Cameron, who infuriated the regime by visiting displaced families in the formerly war-affected north, and demanding an international inquiry into war crimes.

At a Colombo dock on Sunday, Mr Abbott announced Australia would give two Bay-class patrol boats, recently retired from surveillance service in Australia, to the Sri Lankan navy to capture asylum seeker boats before they leave Sri Lankan waters.

''People smuggling is a curse. It is an evil trade … the promises that people smugglers offer are promises of death, not life,'' he said.

Critics have condemned the gift, which will cost Australia about $2 million. Greens leader Christine Milne said: ''The Prime Minister's silence on human rights abuses in Sri Lanka was inexcusable complicity but this is nothing less than collaboration and it is abhorrent.

''I am devastated and heartbroken at the thought of Australia assisting a disgraced government to suppress and control its citizens.''

Labor frontbencher Tony Burke said he wanted to see the detail of the agreement on the use of the ships at sea. Speaking on the ABC's Insiders he said: ''I'm not sure how it works … because you are not dealing with a transit country. There may be some people who claim to be directly seeking asylum.''

The details of the agreement, what materiel the ships could carry, and how they could be deployed, has not been made public, and on Monday, Immigration Minister Scott Morrison refused to say what, if any, limitations Australia had placed on the use of the boats.

''We'll work through those arrangements with the Sri Lanka government,'' he told ABC Radio.

''That is the appropriate place to have those discussions.

''I make no apologies for the fact that we are endeavouring to work with the Sri Lankan Government to stop boats coming to Australia. That is the point.''

Mr Morrison said on a visit to Sri Lanka in December last year, then foreign minister Bob Carr gifted surveillance equipment to the Sri Lankan government to monitor people smuggling activity.

He said Senator Carr had discussed providing other assistance, including the kind of patrol boats the Abbott government was providing.

"I don’t recall any great hubbub about that at the time from the government and members of the Labor Party. We’re continuing that approach,’’ he said.

Opposition Leader Bill Shorten said he was not "specifically aware'' of the outcome of the former Labor government's discussions with Sri Lanka.

Responding to Greens criticism that the gift represents Australian collaboration in Sri Lankan human rights abuses, Mr Morrison said he would not take advice from the party.

''The Greens' approach was tried by the previous government. The softening of our borders and all of that, they tried it all and over 1100 people ended up dead. I am not going to repeat the mistake of the previous government in being led around by the Greens,'' he said.

Opposition immigration spokesman Richard Marles said on Monday that Labor supported co-operation with neighbours, but it was ''deeply concerning'' that there appeared to have been no limits placed on how Sri Lanka used the vessels.

While acknowledging ''progress'' on human rights in the country, Mr Marles said the boats must be used only to combat people smuggling.

''There needs to be a clear understanding with the Sri Lankan government about the terms on which these vessels will be used,'' he said.

The chief of Sri Lanka's Navy, Vice-Admiral Jayanth Colombage, said the ships would improve its surveillance capabilities.

''The ships will be put into good use to maintain the freedom of the Indian Ocean from any kind of maritime crime,'' he said.

Mr Abbott dismissed concerns that Sri Lanka could not be trusted as a partner in stopping people smuggling.

Four Sri Lankan sailors including a senior officer are under arrest on suspicion of being key players in the country's largest - and most profitable - smuggling racket. More are being investigated.

Sri Lanka, as host of the biennial Commonwealth Heads of Government Meeting at the weekend, has faced intense scrutiny over its human rights record, particularly allegations of war crimes committed by government forces at the end of its civil war in 2009, and of continuing abuses, including abductions, torture and extrajudicial killings by state forces, land seizures and repression of political dissent.

A report by the United Nations found in the final months of fighting credible allegations of violations, ''some of which would amount to war crimes and crimes against humanity'', committed by Sri Lankan government forces and the rebel Tamil Tigers.

And Australia told Sri Lanka at the UN last year that it must ''take action to reduce and eliminate all cases of abuse, torture or mistreatment by police and security forces … and eliminate abductions and disappearances''.

But Mr Abbott said he had come to Sri Lanka ''to praise as much as to judge'' and that significant progress had been made since the conflict. ''I welcome the opportunity that Sri Lanka has had to showcase itself to the world.

''Sri Lanka has come through many troubles but today there is more freedom and more prosperity. I'm here as a friend, I'm here as the representative of the country that wants to do the right thing by Sri Lanka.''

By contrast, Mr Cameron criticised reconciliation efforts and continuing abuses, allegedly at the hands of state security forces.

He infuriated President Mahinda Rajapakse by visiting the former war zone city of Jaffna, meeting the families of people who had disappeared, and those whose land the military had seized.

Mr Cameron said Sri Lanka had enormous potential but the Commonwealth had a responsibility to speak frankly to its members.