A Labour peer has quit the party in a row over transgender rights.

Lord Moonie was suspended after an investigation was launched into complaints of alleged transphobia.

But he announced he was instead resigning to "save them the trouble" and would "carry on campaigning for women".

As Lewis Moonie, the psychiatrist and community medicine specialist was Labour MP for Kirkcaldy from 1987 to 2005 and served as defence minister under Tony Blair. He was awarded a life peerage on leaving the Commons in 2005.

He had earlier faced a reprimand for retweeting an image relating to transgender women using female toilets which was criticised for implying approval of violence against transgender people.

On hearing of his supsension, he tweeted on Tuesday: "I’ve resigned from the Labour Party today. I was accused of transphobia by the usual suspects, and told I must attend a disciplinary hearing. My membership suspended too.

"Not really up to fighting it so I’ve saved them the trouble. I feel free to carry on campaigning for women."

It is understood that the Labour investigation was at a preliminary stage and has not yet been referred to a disciplinary hearing. HIs resignation from the party means it cannot go forward.

The letter said the party had received complaints about him sharing and posting transphobic content on his social media accounts.

Among social media posts understood to have sparked anger were tweets referring a transgender person as "a c**k in a frock" and a Facebook comment about smear tests for trans women asking "how the f*** do you smear test on a penis? On second thoughts I'm willing to try".

(Lewis Moonie/Twitter (Lewis Moonie/Twitter)

Lord Moonie said he was "scarcely broken hearted" about leaving the party.

The 72-year-old peer has been involved in repeated spats on social media over trans rights and the issue of access to female-only spaces like public toilets.

In recent posts, he set out his view that "trans women are men" and describing as "delusional" the concept that men in transition become "members of the female sex".

"Trans women are and remain men," he wrote. "No less valid as individuals, just not women. Ever."