Hope Hicks, one of the closest aides of US President Donald Trump, is resigning as the White House communications director.

Hicks, 29, is leaving the White House after serving Trump for three years in various capacities. This included being his campaign spokesperson and Director of Strategic Communication when Trump was sworn in as the president on 20 January 2017.

The announcement of her resignation came a day after she testified before the House Intelligence Committee on allegations related to the Russian interference during the 2016 presidential campaign.

The White House did not announce her exact day of resignation.

“Her departure is to be determined but it will be sometime in the next few weeks,” it said.

Hicks is Trump’s longest serving aide, having worked with him before he announced his candidacy, through the campaign, and into the second year of his administration.

After three years, she approached Trump and told him she wanted to leave so she could start exploring opportunities outside of the White House.

On his part, Trump was effusive in his praise for Hicks.

“Hope (Hicks) is outstanding and has done great work for the last three years. She is as smart and thoughtful as they come, a truly great person,” Trump said.

“I will miss having her by my side but when she approached me about pursuing other opportunities, I totally understood.

I am sure we will work together again in the future,” he said.

Her role evolved from what was initially considered to be an unconventional press and communications aide to formally being announced White House communications director in the summer of 2017.

In this position, Hicks led strategic messaging for administration priorities such as the historic passage of tax reform and worked with Press Secretary Sarah Sanders to stabilise the press and communications teams after initial phases of transition.

“There are no words to adequately express my gratitude to President Trump. I wish the president and his administration the very best as he continues to lead our country,” Hicks said in a statement.

The White House said Hicks is a “valued adviser and counselor to the president and other senior administration officials”.

“When I became Chief of Staff, I quickly realised what so many have learned about Hope she is strategic, poised and wise beyond her years,” said White House’s Chief of Staff, John Kelly.

“She became a trusted adviser and counselor and did a tremendous job overseeing the communications for the president’s agenda, including the passage of historic tax reform. She has served her country with great distinction. To say that she will be missed, is an understatement,” Kelly said.

Sanders said Hicks would leave behind a void which nobody can fill.

“She is in a league of her own and no one can replace her. Far and away one of the most talented and skilled people Ive ever met and coming to work won’t be the same without her,” Sanders said.

In a little over 13 months of this administration, Hicks is the fourth individual to resign as the White House Director of Communications. The other three being Sean Spicer, Mike Dubke, and Anthony Scaramucci.