Investigation by Karin Goodwin and Andrew Whitaker

THERESA May has been accused of wedding the UK's minority Tory government to the DUP, a party tainted with terrorism, in a desperate attempt to cling onto power.

Last night senior opposition politicians warned that May's pact would allow the DUP, with its past connections to loyalist paramilitary groups, to dominate key areas of UK government policy. The row comes as the DUP is expected to agree a "confidence and supply" deal to sustain a Tory Government.

Key figures in the DUP including former Northern Ireland First Minister Peter Robinson and Ian Paisley were prominent in the early days of the Ulster Resistance (UR), a quasi-paramilitary style group set up to 'protect Ulster'. In later years, UR allegedly imported weapons from South Africa - in collaboration with other loyalist terror organisations - some of which were used in loyalist murders in the 1990s.

May, who mounted an aggressive campaign accusing Labour leader Jeremy Corbyn of links to the IRA, is now facing accusations of hypocrisy.

Corbyn's leading ally in Scotland, Labour MSP Neil Findlay, claimed the DUP deal would give the "hard men of Ulster" influence over UK policy. Findlay predicted May's government will find itself "held to ransom". He said: "It is clear that she will have to fold on a number of policy areas."

Former SNP Cabinet minister Alex Neil also accused the Tories of hypocrisy. "It's absolutely unacceptable that we will be governed by the priorities of the DUP," he said. "If the Labour Party contemplated a deal with an organisation like the DUP the Tories would be at the head of the queue to pillory them."

Pete Shirlow, the director at the University of Liverpool's Institute of Irish Studies, said that while it was important to recognise that the DUP had moved on and had not been directly involved in violence, UR would have been seen as "a menace, a threat". He said: "Some would say they rabble-roused and encouraged."

On CAIN - the acclaimed Ulster University's Conflict Archive on the Internet – UR is described as "a Loyalist paramilitary style organisation which was formed on 10 November 1986 by Ian Paisley, then leader of the Democratic Unionist Party (DUP), Peter Robinson of the DUP, and Ivan Foster". CAIN claims UR was organised into nine battalions and members wore paramilitary-style red berets. Robinson was pictured at the time wearing a red beret, and beside men in military fatigues.

CAIN continues: "In November 1988 there was an arms find in County Armagh and the subsequent arrest of a former DUP election candidate brought accusations of links between DUP politicians and armed paramilitary groups. The DUP claimed that party links with the organisation had ended in 1987. Two members of Ulster Resistance were arrested in April 1987 in Paris along with a South African diplomat. It was claimed that there had been an attempt to exchange information on Shorts' [the Belfast arms manufacturer] missile technology for weapons."

Last year the Police Ombudsman for Northern Ireland published a 157-page report into the infamous Loughinisland massacre in 1994, which saw loyalist gunmen murder six civilians in a bar. Evidence found that guns used in that attack were imported into Northern Ireland by the UR in the late eighties, by which point the DUP had severed links.

Dr Peter McLoughlin, lecturer in politics at Queen's University, Belfast, said: "I think it is fair to say that the DUP under Paisley certainly flirted with paramilitarism." He added: "More importantly, I think many actual members of loyalist paramilitaries would acknowledge that they were partly inspired to set out on the course they did, and commit the acts that they did, by Paisley’s fierce rhetoric from the very outset of the Troubles regarding the need to ‘defend Ulster’ against republicanism. In that way, it’s very hard to divorce the DUP from the past Troubles."

Last night, former DUP leader Robinson denied to the Sunday Herald that he had ever been a paramilitary and claimed photos of him carrying a gun on on the Israel-Palestinian border in the 1980s had been "taken out of context" by opponents. He said the picture had been taken at an event to promote peace organised by the UN. Robinson claimed the DUP was being smeared by those who want to wreck its pact with the Tories.

In a 1986 Panorama interview Robinson described loyalist prisoners as "counter-terrorists" who would not have been involved in paramilitary activity if Britain had dealt with the IRA.

He said to the Sunday Herald: "If anybody takes photographs out of context and they overstep the mark, we'll meet them in the courts". He added: "If anybody suggested I [was a paramilitary] it would be a very good pay day for me ... We encouraged people across Northern Ireland to turn their back on paramilitarism."

However, while experts agree the party and its recent leadership has moved beyond its past, its support base is still problematic. In the run-up to the election, The Loyalist magazine – linked to the Ulster Political Research Group, an advisory body connected to the paramilitary Ulster Defence Association – called on its readers to support the DUP's Emma Little-Pengelly and Nigel Dodds. Both went on to win their seats.

Little-Pengelly is the daughter of former UR member and convicted gun runner Noel Little, who appeared alongside Peter Robinson in the "red beret" photograph. The DUP and Peter Robinson went on to play a major role in the Peace Process and the Good Friday Agreement.