Dan Poulter has become the second former minister to be referred to the Conservatives' new disciplinary panel – after allegations that he behaved inappropriately towards female MPs.
Downing Street confirmed on Sunday that Dr Poulter, who served as a health minister in David Cameron's government for three years, was being investigated.
It comes after former cabinet minister and leadership contender Stephen Crabb was referred on Saturday after admitting he said some "pretty outrageous things" in text messages to a 19-year-old woman who applied for a job in his office.
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Dr Poulter, 39, has been accused of breaching the Tories' new code of conduct, which was published by the party last week after a number of sexual harassment allegations were made against senior figures in Westminster.
Sir Michael Fallon resigned as defence secretary over the scandal on Wednesday night; and two former Labour shadow ministers are also under investigation by their party.
Allegations were made about Dr Poulter by his fellow Tory MP Andrew Bridgen who said he had heard three female Conservatives discussing his behaviour towards them in the Parliamentary tea room.
Mr Bridgen claimed he reported his concerns to a party whip after the conversation in 2010 – six months after Dr Poulter, who also works part-time as a doctor, became an MP.
He said the concerns were not acted upon, and Dr Poulter, the MP for Central Suffolk and North Ipswich, was made a minister two years later.
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Sky News understands the chief whip at the time, Sir Patrick McLoughlin, was not made aware of the allegations made by Mr Bridgen.
Downing Street would not comment on whether Dr Poulter should have been promoted.
A spokesperson said: "The Chief Whip having spoken to Dan Poulter, has referred him to the party's new disciplinary committee for further investigation."
Dr Poulter, who returned to the backbenches in 2015, could not be reached for comment on Sunday morning.
