Sport England is responsible for increasing physical activity and allocates government and National Lottery funding to grassroots projects.
Last summer it wrote to Ofcom to express its “deep concern regarding the recent wave of racist and sexist abuse” directed at England’s women’s football team on social media.
“Sport should always be a place where everyone feels safe and welcome,” said Boardman.
“Those are values worth standing up for. When a space undermines that, walking away is not weakness – it is a responsibility.
“Last summer we urged action on the horrific sexist and racist abuse being levelled at our Lionesses. Alongside these actions, we have to make choices about where we show up as an organisation and where we don’t.”
Last month BBC Sport revealed that more than 2,000 extremely abusive social media posts – including death and rape threats – were sent about managers and players in the Premier League and Women’s Super League in a single weekend, with 82% of abusive posts made on X, formerly known as Twitter.
“X has become a less effective way for us to do our job,” said Boardman. “The tone of conversation has grown increasingly divisive and reductive.
“We recognise that some people and organisations believe staying in difficult spaces and challenging harmful narratives from within is the right approach.
“For Sport England, however, stepping away from X is the right decision. It aligns with our values, supports our commitment to women and girls, and allows us to focus our efforts where they can have the greatest positive impact.
“Tech companies – particularly X – must take greater responsibility for the environments they create and the content they amplify.”
BBC Sport has approached X for comment.
It has previously referred the BBC to a statement posted by its safety account at the start of January which reads: “Anyone using or prompting Grok to make illegal content will suffer the same consequences as if they upload illegal content.”
X owner Musk has said the UK Government wants “any excuse for censorship” in response to a post questioning why other AI platforms were not being looked at.
Last month, UK Sport, the body that funds Olympic and Paralympic sports, signed a contract worth more than £300,000 to give thousands of athletes access to an app that detects and hides abusive posts sent by other users on social media.
Athletes are able to sign up for free and can protect their accounts throughout the Games cycle up to Los Angeles 2028.