One of US President Donald Trump's top aides has resigned amid abuse claims from his two ex-wives.

White House staff secretary Rob Porter said "these outrageous allegations are simply false" as he announced he would step down.

The accusations were first reported in the Daily Mail and include accounts of physical and emotional abuse.

The White House would not comment on a report that Mr Porter, 40, failed to receive security clearance.

Colbie Holderness alleged Mr Porter punched her in the face on holiday in Florence, Italy

His ex-wives, Colbie Holderness and Jennifer Willoughby, both recounted stories of Mr Porter's alleged misconduct.

His first spouse, Ms Holderness, said the White House aide had been verbally and physically abusive.

Ms Holderness, a US government analyst, said Mr Porter had kicked her on their 2003 honeymoon in the Canary Islands.

She also alleged he punched her in the face while they were on holiday a couple of years later in Florence, Italy.

 Jennifer Willoughby told the Daily Mail she filed a protective order against Mr Porter

Ms Holderness supplied a photo of herself with a black eye to the media.

Ms Willoughby, a motivational speaker, told the Daily Mail she was married to Mr Porter from 2009-13.

She wrote about her experiences in a blog post entitled Why I Stayed.

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Squeaky-clean aide

Analysis by Tara McKelvey, BBC White House reporter

Rob Porter was a squeaky-clean aide who made sure that papers landing on the president's desk were in order.

The White House staff secretary also helped the president follow protocol.

At one event in the East Room, for example, Mr Porter stood in the back of the room and gestured to the president, showing him where he was supposed to go in order to sign documents.

Mr Porter's decision to resign - and the allegations against him - have shocked those who know him.

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She said she filed a protective order against him in June 2010 after he allegedly punched the glass of the door at their Alexandria, Virginia, home.

Ms Willoughby told the Washington Post on Wednesday: "He has never faced repercussions that forced him to confront his issues.

"I care about him and want what's best for him, but that doesn't necessarily mean him keeping his job because he needs to face these underlying issues."

Mr Porter rejected the allegations in a statement read by the White House press secretary on Wednesday.

Mr Porter (R) with White House senior adviser Jared Kushner (L) and chief of staff John Kelly (C)

"I took the photos given to the media nearly 15 years ago and the reality behind them is nowhere close to what is being described," he said.

"I have been transparent and truthful about these vile claims, but I will not further engage publicly with a co-ordinated smear campaign."

The Daily Mail reported that Mr Porter did not receive security clearance for his White House job after the FBI interviewed his ex-wives during background checks.

Mr Porter has been romantically linked with White House communications director Hope Hicks

But the White House press secretary refused to be drawn on that issue.

"Background checks involve a complex investigation run by intelligence and law enforcement agencies," Mrs Sanders told reporters.

"As has always been our policy, we do not comment on security clearances. Rob Porter has been effective in his role as Staff Secretary.

"The President and Chief of Staff have full confidence in his abilities and his performance."

Mr Porter attended Harvard with the President Trump's son-in-law Jared Kushner and was a Rhodes Scholar at Oxford University.

He formerly worked for Utah Senator Orrin Hatch, who said he was "heartbroken" by the allegations.

Mr Porter (L), White House chief economic adviser Gary Cohn (2nd L) and White House Press Secretary Sarah Huckabee Sanders

"My staff loved him and he was a trusted advisor," Senator Hatch said in a statement.

"I do not know the details of Rob's personal life.

"Domestic violence in any form is abhorrent. I am praying for Rob and those involved."

Mr Porter's White House role involved working with the president and his chief of staff John Kelly.

Before Mr Porter resigned, Mr Kelly told the Daily Mail the staff secretary was "a man of true integrity and honour".

According to the reports, Mr Porter has recently been romantically linked with White House communications director Hope Hicks.