Senior DUP members believe the party could grow by attracting conservative Catholic voters.

Edwin Poots said that the party's uncompromising opposition to abortion and gay marriage brings it into line with Catholic moral teaching.

The revelations come as the Belfast Telegraph continues its series on a major new academic publication on Northern Ireland's biggest political party.

The Democratic Unionist Party: From Protest To Power, by Professor Jonathan Tonge, recorded interviews with several of the leading figures within the DUP.

Health Minister Mr Poots told the researchers that the party could reach out to Catholics as well as Protestants.

He said: "I actually think there is an educated, conservative Catholic vote out there, which the DUP is probably best placed to pick up. They want to ensure their kids get a good education, they are supportive of the doctrines of their church.

"The doctrines of their church largely coincide with the DUP. So conservative Protestantism and conservative Catholicism have an awful lot in common."

Mr Poots pointed out that, although the SDLP opposed abortion, the party was in favour of gay marriage, while Sinn Fein was in favour of both gay marriage and abortion in some circumstances.

Paul Givan, the DUP chair of the justice committee, takes the same view. "How can you vote for Sinn Féin and the SDLP if you are opposed to gay marriage?" he asked. "Sinn Féin certainly, their stance on abortion wouldn't be in line with the Catholic Church."

But the author of the book has his doubts that the DUP can attract votes from Catholics.

"There is an assumption amongst DUP members that most Catholics adhere to the social and moral conservatism of their church when, like many in the Protestant community, their faith, or at least adherence to church teaching, may be waning" he warns.

DUP members interviewed say they don't canvass in many Catholic areas. "It really is a waste of time going into an area where you get the door slammed and you get insulted and you get shouted at," said Jim Wells, the South Down MLA. Despite canvassing in a mixed area of Newcastle, he found that he got "less than 20 Roman Catholic votes".

Members are also slow to encourage interaction with Catholics. Three-quarters would mind if a relative married a person of a different religion. Despite official DUP backing for shared education, 83% would prefer if their own children were educated with people of the same religion.

Mervyn Storey, DUP education spokesman, questioned taxpayer funding for Catholic schools. "To give, as has been given to the Catholic Church, an absolute right that you can educate your children in those schools, and by the way, the State will also pay for it. There is a contradiction in doing that and then saying, but we will also, at the same time, advocate shared education."

The DUP has consistently opposed homosexual law reform – former leader Ian Paisley once spearheaded a 'Save Ulster From Sodomy' campaign. For many members, opposition to gay marriage and abortion is a core value, and they are keen to find more voters to support their view.

Asked if homosexuality was "wrong", only 23% thought that it wasn't, with a two-thirds majority believing it was. This probably shows some softening of opinion within the DUP in recent years, but opposition to gay marriage would probably be much higher.

When it comes to abortion only 15.3% felt it should be legalised here, while 73% thought it shouldn't. At present abortion is only allowed here in very limited circumstances.

The other issue that Mr Poots regards as a selling point with some Catholic voters is academic selection of primary school pupils. That is also an issue close to the heart of existing members. Asked whether they supported it or not, 81% said they did.

The Democratic Unionist Party: From Protest To Power (by Jonathan Tonge, Maire Braniff, Thomas Hennessey, James W. McAuley, and Sophie Whiting) will be published by Oxford University Press on June 17, priced £55

Voices from inside the party

Ards councillor

"I believe scripturally it (homosexuality) is wrong. I would be against same-sex marriage and civil partnerships as well. I believe that with the Word of God it's wrong. But I also know people who are homosexual, and as a councillor I have worked for homosexuals. I don't discriminate against anybody who comes to me for help. I believe to love the sinner and not the sin."

DUP MLA

"I certainly don't believe that the majority of people in Northern Ireland are in favour of it (gay marriage). I certainly don't believe anywhere close to the majority of my voters are in favour of that. It would be suicidal for me to get up and say I am in favour of this if I was. I'm not, but if I was."

MLA Paul Givan

"How can you vote for Sinn Féin and the SDLP if you are opposed to gay marriage? Sinn Féin certainly, their stance on abortion wouldn't be in line with the Catholic Church."

Minister Arlene Foster

"Inevitably, I get asked the question: 'What about your children'? And what is really frustrating is that you never ask that of any of my male colleagues and that's just the reality. Women are still primary carers for children and therefore there are always questions – do you feel guilty, which I was asked about as well: do you feel guilty going to work?"

Female representative

"I got my child to the bus in the morning at a quarter to eight and I was going to a meeting and wasn't back till ten o'clock. She was in her bed. I didn't see her all day and you feel guilty at times. It is hard to juggle work and home life."

Female councillor

Describing the reaction of others after she became the first woman to be elected in her district: "They can be hurtful, very, very hurtful. When I joined the council, I was going home in tears many a night – till I had to threaten that I was going to take legal action and get a solicitor to look at it."

Belfast Telegraph