Caroline Lucas in Page Three T-shirt protest during debate
Green MP Caroline Lucas has been told to cover up a T-shirt displaying the slogan "No More Page Three" in large lettering during a Commons debate.
She wore the white T-shirt at the start of a debate on media sexism.
Chairman of the session, Labour's Jimmy Hood, interrupted her and told her to "put her jacket back on" and comply with Westminster's dress code.
Ms Lucas picked up a copy of The Sun and waved Page Three, but said she would comply with the ruling.
She added: "It does strike me as a certain irony that this T-shirt is regarded as an inappropriate thing to be wearing in this House, whereas apparently it is appropriate for this kind of newspaper to be available to buy in eight different outlets on the Palace of Westminster estate."
During the debate, the MP for Brighton Pavilion argued The Sun newspaper's Page Three, which features topless models, should be consigned to the "rubbish bin where it belongs".
She expressed her support for the No More Page Three campaign and said the content of the page was not acceptable in a family newspaper said to be seen by 7.5m people each day.
Earlier this year, media mogul Rupert Murdoch, who owns The Sun, hinted on Twitter that Page Three may be replaced with a "halfway house" of "glamorous fashionistas".
Ms Lucas said: "To date, public pressure has secured the most public sign from The Sun's proprietor that the paper might scrap Page Three. But the clock is ticking and we still have not seen any concrete action.
"So if Page Three still hasn't been removed from The Sun by the end of this year, I think we should be asking the government to step in and legislate."
She also called for The Sun to be removed from sale in Parliament until it dropped the photo feature.
Culture minister Ed Vaizey said there were no plans to regulate the content of the press.
He said it was for adults to choose what they read, provided something remains within the law or does not impact inappropriately on the rights of an individual.
He added: "Freedom of expression is a vital part of our society. But, as well as maintaining this freedom, we as a government are committed to maintaining a media that commands respect from the public through high standards and is capable of appropriately protecting the rights of individuals."
Limited rules on member's dress are set out in Erskine May, the official parliamentary rule book. It says MPs should not wear military insignia or uniforms in the Commons and the custom is "for gentlemen members to wear jackets and ties".
However, other standards of dress are expected to be adhered to as a matter of convention.
A House of Commons spokesman said: "By convention members are expected not to use their clothing to display slogans or make debating points - members are expected to make their arguments through their speeches.
"It is for the chair of a debate to make a judgement on whether those conventions are being met."