Giving up a seat for expectant mother and Equalities Minster Jo Swinson, forced to stand during Prime Minister's Questions, could be considered "sexist", a source close to the minister has said.
Swinson, who is seven months pregnant, stood at the back of the crowded Commons chamber during the session.
Jo Swinson said she was happy to stand at PMQs on Wednesday
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On Thursday evening, the MP attempted to diffuse the debate, saying she was happier to stand in the chamber.
The Prime Minister's spokesman said David Cameron would offer his seat to a pregnant woman on a bus and it was "very understandable" to be prepared to stand so that someone in greater need could take a rest.
At a regular Westminster briefing he said: "Take the example of public transport... I think if you see someone who is in greater need of a seat than yourself I think offering that seat is a good thing to do."
Asked if Cameron would offer his seat to a pregnant woman if he was on a bus, the spokesman said: "I'm sure he would."
Pressed on whether that would be a sexist thing to do, the spokesman said: "Offering one's seat to someone who is in greater need than oneself on public transport? I think that's a very understandable thing to do."
Asked if that applied in the House of Commons, he added: "I think in every walk of life if you see somebody who is in greater need than yourself to take a seat then offering your own, that's a very understandable thing to do."
A source close to Swinson told the MailOnline website: "The suggestion somehow that people should be outraged on her behalf is ridiculous. The idea that just because she is seven months pregnant she has lost all ability to stand on her two feet or fend for herself is quite sexist.
'She did not think it was an issue. If she had wanted to sit down she would have asked to sit. She is quite capable of fulfilling her functions as a minister - including standing and walking - while she is pregnant. She is not somehow severely incapacitated."