A US Congressman has resigned amid concerns over his 'discussion of surrogacy' with two former female staff members.

Mr Franks is an Arizona representative who has served as a congressman since 2003.

He will now leave Congress at the end of January.

Republican Trent Franks announced his resignation as it was revealed that the House Committee on Ethics had approved an investigation into the complaints.

The committee said an investigative subcommittee "shall have jurisdiction to determine whether Representative Trent Franks engaged in conduct that constitutes sexual harassment and/or retaliation for opposing sexual harassment, in violation of House Rules, law, regulations, or other standards of conduct".

House Speaker Paul Ryan's office, meanwhile, confirmed Mr Ryan had received "credible claims of misconduct" concerning Mr Franks, and the Republican leader had asked the Arizona politician to resign in the wake of the allegations.

In a statement, Mr Franks said he and his wife previously had a woman act as a gestational surrogate, and highlighted the couple's eagerness to have at least one more child.

He explained: "Due to my familiarity and experience with the process of surrogacy, I clearly became insensitive as to how the discussion of such an intensely personal topic might affect others.

"I have recently learned that the Ethics Committee is reviewing an inquiry regarding my discussion of surrogacy with two previous female subordinates, making each feel uncomfortable. I deeply regret that my discussion of this option and process in the workplace caused distress.

He stressed: "I have absolutely never physically intimidated, coerced, or had, or attempted to have, any sexual contact with any member of my congressional staff.

"However, I do want to take full and personal responsibility for the ways I have broached a topic that, unbeknownst to me until very recently, made certain individuals uncomfortable."

It marked Thursday's second high-profile resignation in Washington, following Democratic Senator Al Franken's announcement that he will resign from the Senate in the coming weeks.

Recent weeks have seen several women accuse Franken - a two-term Minnesota senator and former Saturday Night Live comedian - of inappropriate behaviour and sexual misconduct.

In a speech on the Senate floor, Mr Franken insisted that "some of the allegations against me are simply not true" - but added he could not remain an 'effective senator' while facing an Ethics Committee probe.