Britain has the right to control its borders and turn away the tens of thousands of economic migrants posing as refugees, Theresa May told world leaders today.

At her first United Nations summit, the Prime Minister declared that the 'unprecedented' and 'uncontrolled' wave of immigration into Europe is not in the interests of the UK, the migrants themselves or the countries they leave behind.

Mrs May rejected demands from some UN members and charities for Britain to throw open its borders.

And she criticised the inaction of global leaders that has let the crisis spiral out of control. Government sources said she would stress that – if public support for genuine refugees is to be maintained – the system must be robust in rooting out abuse by economic migrants.

Theresa May (pictured at the UN Assemly today) told world leaders that Britain has the right to control its borders

The UN General Assembly, starting in New York today, will kick off two years of negotiations on a new global policy for migration and refugees. The UN is pressing for wealthy nations such as Britain to create more routes for economic migrants from poorer countries.

But Mrs May stressed that the emphasis must be on the 'right of all countries to control their borders' – not the rights of economic migrants to enter the UK seeking work. Government officials said she wanted the UN to accept this must be one of three key principles on immigration policy.

Crucially, she also demanded a distinction is drawn between genuine refugees and economic migrants. The influx into Europe has been dubbed a 'refugee crisis', but Mrs May stressed many of them are in fact seeking work and should be treated as such – with no automatic right to resettlement.

The third rule she sought at meetings with US President Barack Obama, UN Secretary General Ban Ki-Moon and others is a declaration that refugees should remain in the first safe country they reach. In the case of Syria, Mrs May said this should be Lebanon or Jordan.

At her first United Nations summit, Theresa May (pictured at the UN today) declared that the 'unprecedented' and 'uncontrolled' wave of immigration into Europe is not in the interests of the UK, the migrants themselves or the countries they leave behind

Theresa May (pictured meeting world leaders at the UN today) rejected demands from some UN members and charities for Britain to throw open its borders

Migrants are seen in a make shift camp known as the 'New Jungle' in Calais, France

The PM also pledged tens of millions of pounds more from the foreign aid budget to support education and other projects in countries close to migrant hotspots.

The aim is to drastically reduce the numbers trying to head to the UK by illegal routes.

A restatement of the so-called 'first country rule' will also help Britain after Brexit. Brussels rules say a person must claim asylum in the first safe country they reach inside the EU, and can be sent back there if they travel onwards.

MPs PUSH FOR 'HARD BREXIT' By Daniel Martin, Chief Political Correspondent for the Daily Mail Tory Eurosceptics are lining up to join a new 'hard Brexit' group that will campaign to ensure the Prime Minister does not compromise with the EU. Senior MPs, including former ministers Owen Paterson, Dominic Raab and Sir Gerald Howarth, have signed up to the 'Leave Means Leave' group. They will use their position on the backbenches to put pressure Theresa May to leave the single market completely, retaining full control of Britain's borders and ending the influence of Brussels on legislation. The group was set up by businessman Richard Tice – a leading figure in the Leave.EU referendum campaign group – who called for Mrs May to pull out of the single market even if there was no trade deal. 'Let's be clear: no deal is better than a bad deal,' he said. 'The British people made it clear that they wanted to leave the EU. There should be no compromise on this.' But the new body was savaged by former business minister Anna Soubry, a Remain supporter, who said leaving the EU with no trade deal would decimate industry. Advertisement

Backing of this principle by the UN will reduce the temptation for countries such as Italy, Greece or France to simply wave migrants on to Britain once we leave the EU.

Mrs May told the UN she believes her approach will be 'more effective' than the current system.

She said: 'Across the world today, we are seeing unprecedented levels of population movement and we need to work together to find a better response, which focuses our humanitarian efforts on those refugees in desperate need of protection and maintains public confidence in the economic benefits of legal and controlled migration.

'But we cannot simply focus on treating the symptoms of this crisis, we need to address its root causes too. While we must continue our efforts to end conflict, stop persecution and the abuse of human rights, I believe we also need a new, more effective global approach to manage migration.'

Her comments are a rebuttal to the likes of ex-Labour foreign secretary David Miliband, now head of the International Rescue Committee, who yesterday called for Britain to quadruple the number of refugees it grants asylum to. He said the UK should take up to 25,000 a year.

A report by the Overseas Development Institute has predicted the UK faces 43,000 asylum applications this year – costing the public purse £620million. There were about 39,000 asylum claims last year.

Mrs May also called for a tightening of aviation security worldwide in the wake of terrorist atrocities such as the downing of a Russian Metrojet flight from Sharm el-Sheikh last October and the attacks at airports in Brussels and Istanbul this year. The PM will also use her trip to meet US businessmen in a bid to persuade them to invest in post-Brexit Britain.

Theresa May (pictured at the UN today) criticised the inaction of global leaders that has let the crisis spiral out of control