A new adviser to the Bernie Sanders campaign issued an apology on Twitter for calling Michelle Obama “ugly” in 2009.

Civil rights activist Phillip Agnew joined Mr Sanders' team on 7 March. When other users dug into his tweet history and found evidence that he’d made disparaging remarks about Ms Obama’s looks, he decided to issue an apology.

“I am not my tweets from 2009. Still, words have power to heal & to harm and I acknowledge and apologize for when my words harm. I’ve spent years speaking life and love into my community but I was wrong and I have to be accountable,” he tweeted.

Mr Agnew then went on to post a longer apology and explanation attached to his tweet.

In 2009, Mr Agnew tweeted that “[Michelle] Obama is an odd looking woman,” he wrote. “I’d call her ugly but I don’t want the backlash.”

In the same year, he also wrote that “Michelle Obama is just not pretty” and that he’d “tried to look at her from every angle possible.”

Mr Agnew is the co-founder of the civil rights group Dream Defenders, which formed after the death of Trayvon Martin. Mr Agnew claims that his upbringing played a part in his past statements, but that he has moved past those influences.

“I am writing to own that in 2009, when I was 23, I tweeted stupid comments about Michelle Obama,” he wrote in his statement. “I am sorry for the remarks that I made. I typed them as a young, immature and insecure boy who thought he was forever invisible and ‘invincible.’ My comments were shallow, careless, sexist and cruel.”

Mr Agnew explained that he had been “socialized by false standards of beauty and success,” and that it twisted his thinking.

“And young, dumb Phillip spouted all manner of things that today I absolutely reject and regret,” he wrote.

He believes he has improved.

“As a young community organizer, I have spent hours and days, months and years doing, thinking and being better, privately and publicly,” Mr Agnew wrote. “I've matured, been politicized, and continuously been pushed and challenged by fellow organizers to change and grow into my values. I am still a work in progress.”

Mr Agnew joined Mr Sanders’ team as the Vermont senator’s campaign sought to expand its outreach possibilities into African American communities.