'Nearly 100 war crimes suspects' in UK last year
The Home Office last year identified nearly 100 suspected war criminals who had made UK immigration applications, figures released to the BBC suggest.
The majority of cases involved people already likely to have been living in Britain for a number of years.
Suspects originated from countries including Afghanistan, Iran, Iraq, Libya, Rwanda, Serbia and Sri Lanka.
The Home Office says it is determined the UK doesn't become a "refuge for war criminals".
Human rights groups are calling for more criminal prosecutions in Britain as the courts commonly block deportation on human rights grounds if suspects face torture or death in their home country.
The figures emerged from a Freedom of Information request made by the BBC.
They show that, in the 15 months from January 2012, the Home Office researched nearly 800 cases where individuals were suspected of war crimes and crimes against humanity.
It made "adverse recommendations" against 99 people who had applied for British citizenship, asylum or leave to remain in the UK. A further 16 war crimes suspects had applied to enter the UK.
It follows earlier figures suggesting more than 700 suspected war criminals were identified by UK immigration officials between 2005 and 2012.
Michael McCann MP, chairman of a cross-party parliamentary group to prevent genocide, says the figures reveal the need for greater transparency from the government in cases where war crimes suspects are in the UK.
"The organisation in the Home Office that used to deal with this - the UKBA (UK Border Agency) - was a basket case. It had failed on so many different levels I've lost count," he said.
"I have deep concerns that the Home Office isn't being as forthright as it could be and I think we should be drilling down into these cases in order to give the public of our country that security."
Of the 99 suspects, three were deported last year, 20 were refused asylum and 46 had their citizenship bids turned down but are likely to have remained in the UK. The fate of the remaining suspects is unknown.
In May 2013, five Rwandan men were arrested in Britain suspected of involvement in the 1994 genocide that led to the deaths of an estimated 800,000 people.
Some of them have been in Britain for more than a decade, with one having worked in a care home in Essex.
Three are still in custody and two have been released on bail. The men deny any involvement in the Rwandan genocide.
In 2009, an extradition attempt against four of the men failed after High Court judges ruled there was "a real risk" they would not get a fair trial in Rwanda.
Human rights campaigners say the case demonstrates the challenges faced in dealing with international war crimes suspects in Britain, pointing to a lack of successful criminal convictions.
"The police need more resources to investigate these crimes because it's difficult to investigate them," says Kevin Laue, a legal adviser with Redress, a charity which campaigns to prevent genocide.
"That, in turn, requires more political will and commitment at the higher level for them to be given the resources to properly investigate."
James Smith, from the charity Aegis that works to prevent crimes against humanity, said if extradition failed, prosecution could take place in the UK.
"There's a cost and it is difficult to investigate crimes which took place in another country a long time ago. But if we don't pursue those prosecutions, the UK could become known as a retirement home for war criminals," he said.
Beatha Uwazaninka, a survivor of the Rwandan genocide, said the thought of meeting a Rwandan war criminal "living happily ever after" in the UK caused her "great pain".
"It is very sad especially for survivors who have gone through so much and yet there is no justice," she told the BBC.
"They (the war criminals) should be sent to where they committed the crimes but if they cannot send them to Rwanda, at least they can be tried to the UK. It is sending a message that wherever you go you will face the consequences of what you have done."
The Metropolitan Police says 56 people in the UK are currently subject to war crimes inquiries, although only nine cases were passed on to them by the Home Office.
Mr McCann says the "disparity" between the Home Office and police figures raises a question over whether immigration officials are wrongly identifying people as war crimes suspects.
A Home Office spokesman said: "Anyone accused of these crimes should be put on trial in their home country and we will always seek to return them to face justice."