It is not known how many people have accused Buchanan of bullying, and the specific nature of the allegations has yet to come to light.
A former political editor at the Sunday Express, she was suspended after an investigation was conducted during the general election, according to influential political website Guido.
The director of comms, who describes herself as a "former hack - so basically the full 'poacher turned gamekeeper' experience", has yet to comment publicly.
Top Government Aide Suspended over Bullying Row https://t.co/X2KikUPAkA— Guido Fawkes (@GuidoFawkes) January 13, 2020
Buchanan, a senior civil servant on an annual salary of at least £90,000, has only been in the post since last April.
She is responsible for campaigns, public and media relations, digital channels, stakeholder engagement and corporate communications, and leads a team of about 50.
During her application for the job, Buchanan was judged to have attributes such as "an inclusive and collaborative leadership style" and "highly developed interpersonal and influencing skills".
Commenting on her appointment at the time, Aiken said: "Senior leaders have a critical role in inspiring great performance, providing visible leadership and direction, and nurturing talent and creativity."
Buchanan reports to Tom Walker, interim director-general for decentralisation and growth, and is a senior member of the Whitehall directors of communication group.
However, she is relatively inexperienced when it comes to the culture of the Civil Service, having spent most of her career as a newspaper journalist.
Allegations of bullying are not uncommon at MHCLG.
Almost one in 10 (eight per cent) of the department's staff have suffered from bullying or harassment at work in the past year, according to the latest Civil Service people survey, released last year and relating to 2018.
Only a third (33 per cent) of victims reported the abuse they had suffered. Of those, less than one in five (18 per cent) felt the issue had been resolved, according to the same study.
In a statement to PRWeek today, responding to a request for comment on Buchanan's suspension, an MHCLG spokesperson said: "We do not comment on individual members of staff."
The bullying allegation comes just months after Buchanan, a former special adviser to Theresa May, was awarded an OBE for political and public service in the former prime minister's resignation honours.
From local reporter to Downing Street
Educated at Watford Grammar School for Girls, Buchanan went to Kingston University.
After graduating in 1991 she embarked on a career in regional and national newspapers, reaching the position of political editor at the Sunday Express in 2009.
Little more than a year later, Buchanan left to become head of comms at West Sussex County Council.
During her time there she became involved in a row with the Argus newspaper over the media handling of the memorial service for victims of the Shoreham Airshow disaster, which local newspapers were banned from attending. Buchanan failed in an attempt to get IPSO to censure the newspaper over its coverage of the controversy.
She went on the work for Liz Truss during the Conservative MP's brief stint as Justice Secretary, before moving to Number 10 in August 2017 as head of political press.
Buchanan left Downing Street last April to take up the role of director of comms at MHCLG.
She has previously described her stint at Number 10 as a "challenging time", but insisted that she left "for family reasons".
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