Fiona Mactaggart knows a thing or two about coming out.

But in her case, the revelation was about her multiple sclerosis and infertility, which she disclosed in a Commons debate in 2000.

Nevertheless, the Labour MP and shadow equality minister says that MPs must feel “safe” in order to be open about personal aspects of their lives.

However, she despises a liar and says the thing that bothers her most about whispers that she is a lesbian is the implication that she is not being honest.

Ms Mactaggart, 57, has been the MP for Slough since 1997 and was an NUS secretary, teacher and Liberty executive chairman before becoming an MP.

She was a junior Home Office minister between 2003 and 2006 and was named shadow equality minister in October. Her pet subjects as an MP have been immigration and women’s issues, especially prostitution.

She admits she hasn’t “led” on gay rights but has always supported the issue.

“I’ve always supported gay rights. I … haven’t led on it. Why? Because I don’t know anything special. On the bits where I do know something special, I’m happy to speak. But usually, on gay rights, I’m just part of the ‘poor bloody infantry’. And that’s fine, it’s a fine place to be if you’re working in solidarity with colleagues who know more, for whom it’s their number one issue.”

However, her history as a primary school teacher and later a lecturer on education informs her views on homophobic bullying.

“Firstly, you need to give teachers resources. Secondly, schools need clear policy about all kinds of bullying and particular this one.”

Bullying can be eradicated completely, she maintains. “You see schools where it really doesn’t happen. . . . it’s like saying can you ever get rid of petty theft? I think you can. It will still occur on the margins perhaps but why do the big stores always prosecute? Because they know that having a clear, explicit policy where everyone who goes in the store knows the policy changes people’s behaviour.

“It’s equally true of any form of bullying in my view. I’m not one to give up in the face of ‘oh, it’s too hard’. Things are hard but hard’s there to be dealt with, not to be avoided.”

Ms Mactaggart cites “feeling safe” as a key theme for gay equality, especially in the case of LGBT politicians: “You need people to feel that their career, family and life isn’t going to be threatened and unpicked.”

She said: “You don’t need to be as brave as Chris [Smith, the former Labour MP] was, but guess what, life is easier when you don’t stick your head out. The tall poppies get their heads cut off and it is easier to hide in a crowd.”

But she added: “I think the really terrible thing in politics is to tell lies. I think that’s the thing that rightly, voters will not forgive. I think that dissembling, pretending to be other than you are, that’s the unforgivable in most people’s views.”

Ms Mactaggart is not a lesbian but says that the fact she lives with a woman has been used by political opponents.

She said: “Certainly my opponents in Slough, on the doorstep, have suggested I’m a lesbian. The thing that makes me angry is not being accused of being a lesbian but the implication that I’m a liar. If i was a lesbian, I wouldn’t have any hesitation about being out.

“It was Conservative canvassers on the doorstep. It wasn’t printed anywhere. I gather, secondhand, that a Conservative candidate stopped elements within her party publishing a leaflet saying [that I was a lesbian].

“As I said, I came out about having MS and I know that feels different, but as a politician, actually, people thinking that you might end up in a wheelchair, might be a bit crippled, might have intellectual impairment, is kind of high risk. They might think, ‘why should I vote for her?’.”

Her admission of having MS and being infertile came out during a Commons debate on stem cell research in 2000. She had two frozen embryos and while it was considered too late at that stage to use them in fertility treatment, she says they could have been used to research her MS.

“It seemed to me that this experience was the kind of thing which might move some members of parliament’s view. So I think in moments like that, you have to feel safe. And actually I didn’t always [feel safe] talking about this. One of the Conservative MPs said that infertility was a social disease.”

Gay marriage is usually one of the topics which elicits the most reader interest in PinkNews.co.uk political interviews. Ms Mactaggart said: “I think everything should be equal but when I look at the difference between civil partnerships and marriage, the main difference seems to be that adultery isn’t grounds for a divorce.

“I don’t know… I just think we have to talk about it, listen, find out.

“I have no problem with calling it marriage. I honestly don’t feel very strongly about it. But I do think there are interesting issues about the actual differences in civil partnerships. like, for example, the issue of infidelity. . . I don’t know. But I think you need to address not just the name. most of the debate I’ve seen hasn’t explained beyond [that].

“Ed Miliband said that this is a matter the Labour Party should take very seriously. And I think he’s right. We should be part of the debate. We’ve been at the cutting edge of changing the law to provide rights for gay people and I want us to stay at that cutting edge.”

Faith organisations should not be forced to hold ceremonies for gay couples, she says.”While I think the state could properly legislate for civil marriage for gay people, and I have no reservations about that, I think requiring religious organisations to offer religious marriage to gay people might interfere with their rights.”

The coalition government met with gay rights groups in the summer to discuss the future of civil partnerships. Although Ms Mactaggart is more reticent than Mr Miliband and Liberal Democrat leader Nick Clegg on the subject, Labour won’t get another shot at persuading the LGBT community to vote for it until 2015.

When asked how the party can win back support, including from gay voters, she said: “Gay people felt the same as everyone else. They were worried about the economy, felt burdened by taxes, were stressed at work and didn’t feel we had a clear vision of where to go to next. I don’t’ think your sexual preference determines your view in any way.

“Our route back to government won’t be through this lot making mistakes – although they will – it has to be a recognition that actually, most people want to be able to get on with their own lives and have the support that’s necessary to be able to do that. But not to be nannied or nagged. I think we got a bit nannying and naggy. I don’t think we meant to. But I think people did feel that a bit.

“What we need to do is to demonstrate that we have a clear picture of how to run an economy well where people can expected to succeed and do well at life but we also have to provide the support to ensure people can thrive in a way that’s equal for everyone.

“I think it’s going to take time to get there. We also need a real relationship with voters. I think that’s why I am still a red dot in a very blue sea because of that very real relationship with voters.

“When they saw Tory canvassers on the doorstep saying that I was a lesbian, frankly, the people at the other end just didn’t care. They just didn’t care because they thought, ‘she stands up for us. do we mind? Not a bit’.”