56-year-old Vaz, the longest serving Asian MP and chairman of the House of Commons Home Affairs Select Committee, sparked the controversy by commented upon May's "thin" appearance and suggesting her stressful job may have caused weight loss.
"A bit worried about Home Secretary she is looking a bit thin these days. A new diet or pressure of work," the influential parliamentarian wrote on Twitter.
The comment has sparked anger among a number of women MPs, who labelled it as "patronising" and "unpleasant".
"I thought it was rather silly and thoughtless remark from Keith. I know Keith, he is not by nature unpleasant, but I think this remark just came across as rather patronising. I'm reasonably confident as a woman in politics who has had to bear the brunt of comments about my own weight, that actually this is something that is frequently dished out to women MPs that isn't done to the same extent to men," Conservative MP Caroline Nokes said.
Equalities Minister Helen Grant added: "She looks fantastic, she is fantastic. She works incredibly hard. Would the same be said of a male MP?"
Harriett Baldwin, Tory MP for West Worcestershire, said she was sure the Labour MP "would apologise if he thought about it".
May, 56, is believed to have lost some weight over the last year, working out regularly and going mountain climbing in Switzerland.
The Home Secretary is fiercely protective of her private life, rarely giving personal interviews.
There is also speculation that she could be a credible successor to David Cameron as Conservative party leader.
A spokesman at her office said she did not wish to respond to Vaz's remarks.
Vaz's office has also chosen not to issue any statement on the comment.
London: British Indian MP Keith Vaz has evoked sharp criticism from his female counterparts after allegedly making a 'sexist' remark about Home Secretary Theresa May, on a popular social networking site.
First Published: Thursday, February 14, 2013, 19:04