A Stevenage councillor who asked if there would be a "space free at the Windsor's beer garden" on the day Prince Philip died has quit the Labour Party after an investigation was launched into her tweets.

Councillor Lizzy Kelly, who represents the Bedwell ward, was elected to Stevenage Borough Council in 2018 as a Labour representative, but said she no longer felt welcome in the party.

Cllr Kelly added she would serve her constituents as an independent until her term ends in May 2022, after tweeting a screenshot of a notice of investigation on December 1.

The email sent to Cllr Kelly insisted there was not an assumption of guilt during the investigation, and the Labour Party had identified a complaint, adding it was "important that these allegations are properly investigated".

However, in response, the councillor said the investigation was the "last in a series of things" which suggested she was "no longer welcome" in the party as a socialist.

The notice of investigation included two screenshots of her personal Twitter account, which formed the basis of the complaint. One, sent around 20 minutes after the Duke of Edinburgh's death was announced in April, read: "Does this mean there's a space free at the Windsor's beer garden booking on Monday evening?"

The second tweet under investigation was a retweet which read: "Thinking of the queen today, it's never easy when your cousin dies."

In response to the investigation, Cllr Kelly said she had cancelled her membership to the Labour Party, and criticised the party for investigating "random joke tweets" about the Monarchy amidst alleged "inaction" on transphobia and Islamophobia.

In a reply to the notice of investigation, posted online by the councillor, she wrote: "Those are indeed my tweets. I was unaware being royalty was a protected characteristic so didn't realise I was in breach of any rules.

"In any case, this notice of investigation is the last in a series of things which have made it clear that I, as a socialist, am no longer welcome in the Party.

"The Party's inaction on abuse of trans and Muslim members by MPs on social media, while apparently having enough capacity to investigate members based on random joke tweets and the class system it entrenches, also makes it a community I no longer wish to be a part of."

She confirmed that she would continue to represent her constituents in Bedwell until her term is complete in May 2022.

In a follow-up tweet, she added: "It's not my fault the Queen f***ed her cousin!"

When put to the Labour Party, they declined to respond to Cllr Kelly's criticism.

A Party spokesperson said: "The Labour Party takes all complaints seriously and they are fully investigated in line with our rules and procedures and any appropriate action is taken."

Cllr Kelly has since made her Twitter account private, and did not respond to a request for comment.

Stevenage Labour group also did not respond to a request for comment.