A married former cabinet minister sent a young woman sexually explicit messages after rejecting her application for a junior role in his parliamentary office, a Telegraph investigation can disclose.

Stephen Crabb, a devout Christian who stood for the Conservative leadership last year, admitted saying "some pretty outrageous things" to the woman after interviewing her for a job, and that the messages "basically amount to unfaithfulness".

This weekend a friend of the woman said they saw messages in which the father-of-two "said he wanted to have sex with her". The friend accused the MP, who was a government whip at the time, of "abusing his position".

Mr Crabb, 44, said that the pair later met on "several occasions" for drinks and that the messages were sent "from both sides" with the knowledge that "nothing like that was actually going to happen between us."

The disclosure comes after a Telegraph investigation separately uncovered a series of allegations of MPs abusing or bullying staff, amid wider concern about the treatment and welfare of employees in Westminster.

Last night Sir Alistair Graham called for the Commons' "respect" policy to be urgently extended to govern relationships between MPs and their staff, after the investigation exposed a gap in the rules.

There is no suggestion of similar allegations against Mr Crabb. However the woman's friend said his advances represented an "abuse of his position of power" as an MP who had been approached as a prospective employer.

"It's just absolutely awful and of course she never reported it," the friend said.

The disclosure is the second time Mr Crabb has been revealed to have sent explicit messages to a young woman while married. Shortly after he withdrew from the Tory leadership race last summer it emerged that he had sent sexually charged messages to another woman during the run up to the EU referendum.

In one late-night exchange Mr Crabb, the then Secretary of State for Work and Pensions, told her he wanted to kiss her “everywhere” and asked her to call him, it was alleged last year.

Mr Crabb pictured with his wife Béatrice in October 2015 credit: Elliott Franks

It was also claimed that he described a sex act he wanted to perform, prompting the young woman to ask what he was going to do about “your downstairs situation?”.

The separate episode disclosed by the Sunday Telegraph took place in 2013 after the woman concerned applied for a job in his office.

Shortly after the interview, at which other staff were present, Mr Crabb is understood to have used the woman's mobile number to send her explicit messages.

Her friend said: "He interviewed my friend, didn't hire her and then used her number to 'sext.'

"I saw the messages he sent her in which he said he wanted to have sex with her."

The separate episode disclosed by the Sunday Telegraph took place in 2013 after the woman concerned applied for a job in his office credit: Chris J Ratcliffe/Getty Images

While campaigning for the leadership of the Conservatives Mr Crabb presented himself a family man, emphasising his reputation as a candidate with strong “values” and integrity and sound judgment.

He has been married for 20 years to his university sweetheart, Beatrice, who works in his constituency office.

This weekend Mr Crabb admitted that "for anyone who is married or in a relationship, these type of message[s] with someone else basically amount to unfaithfulness and are wrong and hurtful."

He said in a statement: "The interview ... was conducted professionally and transparently, with other staff present, and any suggestion to the contrary is simply false. I have recruited dozens of staff members over the years and the process is always in accordance with good employment practice."