The Ulster Unionists have fewer Catholic members than the DUP, a new book on the party reveals.
Just 0.3% of the UUP is Catholic, even lower than the DUP's 0.6%, according to The Ulster Unionist Party: Country Before Party by Prof Tom Hennessey, Prof Jon Tonge, Maire Braniff, Prof James W McAuley, and Sophie A Whiting.
"In each party you could count the Catholic members on the fingers of your hand, but it will surprise many people that the DUP is ahead of the Ulster Unionists," Prof Tonge said.
He said it was surprising that the UUP had no programme in place to attract Catholic unionists as most members would like a more religiously representative party. "Both unionist parties are currently beyond the pale to Catholics," he added.
Around 1,000 UUP members were interviewed by the authors.
Prof Tonge said the party was considerably larger than the DUP, boosting a membership twice the size. However, while almost a third of DUP members claimed to be "very active", only one in five UUP members did.
The party's strength was in Northern Ireland's least populated county, Fermanagh, where around 20% of members lived compared to 8% of DUP members.
Prof Tonge said the UUP urgently needed to recruit in the more heavily populated counties of Antrim and Down. He revealed that, contrary to popular myth, the UUP had recruited young people in recent years.
"Fifteen per cent of its members joined in the last seven years. The party has been very successful in Queen's and the Ulster University. Where it needs to do better is with ordinary, non-university young people," he said.
The UUP boosts more women members than the DUP - it's 66% male to the DUP's 72%. But Prof Tonge said the centralised nature of the DUP meant greater control over candidate selection by the leadership with women heavily promoted.
"The rise of Arlene Foster to become Northern Ireland's first female leader is symbolic of the DUP's deliberate attempts to modernise the image of the party in the face of their unionist rivals," the book states. "Whether Arlene Foster would have been able to rise through the ranks of the UUP will never be known, but is still a question worth asking."
Although the party's politicians are increasingly liberal on the issue, only 29% of UUP members support same-sex marriage. However, 52% believe Northern Ireland should have the same abortion laws as Britain.
Whereas Free Presbyterians are the largest denomination in the DUP, they account for just 0.1% of the UUP, which is split almost evenly - 43% to 42% - between the Church of Ireland and the Presbyterian Church. UUP members are religious with 45% attending church weekly, although that's lower than the DUP's 59%. Almost six in 10 would mind a religiously mixed marriage in the family a little or a lot.
The Orange Order's influence in the party is on the wane. Only 27% of councillors are members compared to 54% in the DUP, and 20% of MLAs (62% in the DUP). Around 35% of both parties' members are in the Orange Order. Just over half of UUP members would transfer to the DUP in elections. A third said they would give a lower preference to the SDLP and 10% to Sinn Fein. Once an integrationist party, the UUP is now very pro-devolution which has 83% membership support compared to 12% for direct rule.