Counselors reacted angrily after Stella Creasy of Labor was told they would no longer be able to bring their three-month-old son to the Commons room.
The mother of the two children said Parliament should draw in the 21st century after being sent an e-mail by law enforcement officials banning bringing children to meetings.
Commons spokesman Sir Lindsay Hoyle was forced to urgently explain the rules because babies were allowed in the room earlier.
Ms Creasy received a warning after bringing baby Pip into the Westminster Hall debate on Tuesday, when she was seen as “as good as gold” and praised by the MP.
The Walthamstow MP, who has no cover for women, said it appeared that “mothers of all women in parliament should not be seen or heard”.
“It’s strange to me because I have two kids and I took them all into the room where I have to make sure my representatives have representatives,” he told Sky News.
“I think it represents a way you can’t win because if I had a cover for expectant mothers it would be another matter, and I don’t want to and I don’t want to change my people.”
Pip, who is breastfeeding, goes to Commons regularly, as does Ms Creasy’s eldest daughter.
Labor MP Alex Davies-Jones wrote to Sir Lindsay to “expedite” the rules, saying the warning had left him and other women “very worried”.
Davies-Jones said the warning appears to be “contrary” to Sir Lindsay’s assurance in January last year that she would “not be offended” by a mother who chose to breastfeed her baby in the living room.
Caroline Lucas, MP for Green, said the law is “absurd” and “should be challenged”, adding that infants are “less disruptive than most retrospective”.
Ms Creasy received an email from the secret secretary to the Deputy Speaker Dame Eleanor Laing after the argument, in which Pip was seen as quiet and polite throughout the process.
Former Tory minister Paul Maynard told the controversy: “I thank Pip for making the wise decision to sleep on his mother’s talk.
He slept soundly, as we all see, it was probably a wise decision for him.
Labor Director Pat McFadden added: “I also thank our very young member, who has been in the debate and has always been as good as gold.”
But, in the email, Creasy was referred to the MPs’ book section, which was changed in September, saying “he should not be in the room with your child”.
Deputy Prime Minister Dominic Raab said he was “deeply saddened” by Ms Creasy, but added that the decision was up to the House authorities to act.
He told BBC Breakfast: “I think we need to make sure our work reaches the 21st century, and we can allow parents to adapt their careers to the family time they need.
“When you see your friends and their children getting involved in politics, I always think it ‘s good for the community.
“Whether it is appropriate in the room, there have been differing opinions on this matter, it will be up to the House officials to decide, but it will not interfere with or hinder my work.”
A spokesman for the House of Commons said the government was “currently in talks” with Creasy on the matter.
In late September, the newborn Creasy was arrested for her as she woke up in the room to ask Jacob Rees-Mogg to ensure that new women were supported and not “reprimanded” on their way back to parliament.
The Commons leader responded that the rules were “clear and consistent with the rules”.
Former Liberal Democrat leader Jo Swinson is believed to be the first MP to take his son to a contestant room during a debate, when he laid his son on the green Commons benches in September 2018.
Meanwhile, Leicester West MP Liz Kendall said she had resigned from her parliamentary job and her future position for a while next year when she had a new baby through surrogacy.
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