Ivanka Trump praises Theresa May as they meet in New York

Donald Trump's daughter Ivanka has hailed Theresa May for her "remarkable leadership" in the fight against modern slavery, as she vowed the US would join Britain in a "full-throated call" for international action to end the crime.

Ms Trump joined the Prime Minister and United Nations Secretary General Antonio Guterres at a special meeting of countries from across the world to discuss what Mrs May described as the "scourge" of forced labour and human trafficking.

Chairing the meeting, Mrs May announced that the UK will host an international summit of chief prosecutors in the spring of 2018 to discuss a co-ordinated response to the problem.

She told the meeting on the fringe of the UN General Assembly in New York that Britain will double its aid spending on modern slavery to £150 million, enabling more collaboration with the home countries of trafficked people and the transit states which they pass through.

"We gather here today united in our determination to eliminate the scourge of forced labour, modern slavery and human trafficking," Mrs May told the meeting of ministers and leaders from countries including Spain, Saudi Arabia and the Vatican City.

"Modern slavery exists in all our societies, it respects neither borders nor jurisdictions, its victims are subject to the most appalling mistreatment and exploitation."

She urged the nations of the world to join together in declaring: "We will not tolerate these crimes in our societies."

Mrs May said Britain was committed to training specialist investigators and frontline police officers to develop the expertise to prosecute complex slavery cases and offer support to traumatised victims.

Ms Trump offered "many thanks to the Prime Minister for her remarkable leadership".

And she told the meeting: "We can't stand by in silence. We join you today in a full-throated call for enhanced international co-operation to tackle modern slavery in all its evil forms.

"The Trump administration will continue to make this a priority and work with your governments to identify and implement solutions to end these crimes once and for all."

Ms Trump said: "This is a call to action, a call for the global community to address the greatest human rights issue of our time."

Mr Guterres, a former prime minister of Portugal and UN high commissioner for refugees, said: "We are dealing with the multi-nationals of crime and powerful people. Why are we able to arrest drug lords and never the lords of human trafficking?

"If I may be cynical, I would say that when I was in government, I always thought that my children could be victims of drugs but I never thought my children could be victims of trafficking. That is probably why decision-makers around the world never take this problem so seriously."