The director of Human Rights Watch's refugee programme has launched a stinging attack on politicians for their language about migrants.

In a blog post, Bill Frelick referred to British Foreign Secretary Philip Hammond's recent comment about migrants "marauding" around the Calais area and Prime Minister David Cameron's charaterisation of migrants as a "swarm". He also referred to the front-running Republican presidential candidate in the US, Donald Trump, who accused the Mexican government of "forcing their most unwanted people into the United States ... criminals, drug dealers, rapists, etc", and to Australia's Prime Minister Tony Abbot, who said earlier this summer that Australia would not take Rohingya migrants adrift after fleeing persecution in Thailand and Malaysia: "Australia will do absolutely nothing that gives any encouragement to anyone to think that they can get on a boat."

Frelick wrote: "Rancorous, prejudicial and callous discourse from people in positions of great political leadership or prominence risks stoking a climate of xenophobia that in Europe has already led to attacks on migrants and asylum seekers in Germany, Greece, Italy, Hungary, and elsewhere.

"Irregular migration is a serious challenge, but it can be addressed rationally and fairly. This can only happen, however, if the rhetorical heat is turned down a few notches and migrants are not used as demagogic red meat for populist scaremongering."

He called for "fairer burden sharing" among countries and for "asylum systems and border controls that don't sacrifice due process and human dignity".

Frelick concluded: "For our leaders to coarsen the way they speak about migrants not only dehumanises 'them, the other, the stranger', but also threatens to harden the hearts and close the minds of those of us who have had the good fortune to have been born and to live our lives in homelands of comfort and peace."

Labour leadership candidate Yvette Cooper has also criticised Mr Hammond's language, saying in an interview with The Guardian: "The government's impractical and frankly shameful response to Calais is unacceptable. We have the spectacle of a clueless foreign secretary using dehumanising language about people, including many who have fled the conflict in Syria, rather than putting forward a proper humanitarian plan befitting a proud and outward-looking country like Britain."

She called for the government to accept more refugees and for the UN high commissioner for refugees (UNHCR) to be tasked with registering asylum seekers camped at Calais.