The Liberal Democrat MP Layla Moran has announced she is in a “really happy, loving, stable relationship” with a woman, saying she decided to go public after being approached by journalists.

The MP for Oxford West and Abingdon said she found attributing labels to people’s sexuality contrived, but that the term she most identified with was pansexual, meaning she is attracted to people regardless of their sex or gender identity.

Moran, who is thought to be considering a bid for the Lib Dem leadership, said she and her friends had been approached by newspapers that wanted to run stories about her relationship. “That itself is why I’m coming out now because it is a new year and we need to approach the decade fighting these equalities issues on the front foot,” she said.

“If I am going to be outed I want it to be on my own terms,” said Moran. “I’m really proud of it. I’m in a really happy, loving, stable relationship. She’s amazing and I’m really lucky.”

The MP said that in some ways acceptance of the LGBT community had gone backwards in recent years. “It’s 2020 now. How far has society really come?” she said. “It would be nice to think that everything was sorted with equal marriage and that we’re all accepting. But we also know that transphobic and biphobic hate crime has gone up.”

Moran said many people had told her that being in a same-sex relationship could damage her career, but that she hoped they were wrong, citing the former Scottish Conservative leader Ruth Davidson and the former Conservative education secretary Justine Greening as role models.

Moran met her girlfriend, Rosy Cobb, the Lib Dems’ former head of press, through work. Cobb was suspended by the party during the general election after being accused of forging an email.

Moran said the she and her girlfriend had spoken to the Liberal Democrats’ welfare officer about any possible conflicts of interest when they started their relationship, but were told there was no problem. Addressing Cobb’s suspension, she said: “She no longer works for the party and she is not going back, so there is a line completely drawn.”

She said she had not been aware of the details of the case until Cobb was suspended. “At that point I went into girlfriend mode. My job is to support her through a really difficult and painful time,” she said.

“Then people were saying to me that I should call it off with her because it wouldn’t be good for me, but I said no. You don’t abandon people when they are going through a tough time. But I am absolutely convinced that, had she been a man, they would not have said that.”

In March, responding to rumours, Moran issued a statement in which she said she and her ex-boyfriend had been arrested and detained in 2013 for assault and breach of the peace following a row in which she slapped him.

“I think in this day and age that people expect transparency and openness from their politicians and it has never been more true that people don’t trust what we say and what we do,” she said on Thursday.

“I’ve heard people say time and time again, ‘you’re all the same, you’re all liars’, and I dare say that Boris Johnson refusing to answer very basic questions about his life just makes it seem like that’s how all politicians are.” The prime minister has previously refused to say how many children he has.

“I think there’s a very different narrative that we should be telling as politicians, which is that life is not black and white,” said Moran. “We’re all human, but that shouldn’t detract from our ability to fight for other people on a very personal level.”