Ms Hobsbawm said that Hobsbawm Marketing and Media Communications was ruined financially after signing a lease in 1998, which it reassigned to the LA-based film company, Myriad Productions in 2002. Writing in the New Statesman she says: "The cause was the financial equivalent of a tsunami (as in an unforeseen and huge bad debt).
"The culprit was an LA-based film production company that sub-let an expensive property from us several years ago after providing impeccable financial references. It suddenly abandoned Britain last year just as the film tax breaks dried up, leaving my company owing the rent."
The production company, which made the 2003 film Being Julia starring Annette Bening, left Britain due to the uncertainty created by changes to the system of tax breaks for films introduced by the Treasury.
One of the best connected public relations consultants in the country, Ms Hobsbawm is the daughter of the Marxist historian Professor Eric Hobsbawm and the best friend of Kimberly Quinn. She reportedly briefed the media on her friend's behalf when her affair with David Blunkett became public. Ms Hobsbawm is now practising as a solo public relations consultant for the first time in more than 10 years.
Now she writes: "I'm free from overheads and employees as, last month, my old company, HMC, was wound up despite being profitable and successful.
"Without the option to keep the HMC brand I decided to jettison the PR agency life completely in favour of a new venture and solo consulting."
Ms Hobsbawm has already attracted some high-profile clients, including Transport for London and Time magazine.
In the autumn, she is also launching a new media monitoring business called Editorial Intelligence, which will provide information to journalists and PRs. She says the new service will combine "the consulting and analysis of a think-tank with the accurate data of a directory and the inside scoop of a newspaper".
Ms Hobsbawm and Ms Macauley, who met at Camden School for Girls, set up HMC, originally called Hobsbawm Macauley Communications, in 1993, to pioneer a new brand of "integrity PR".
Their clients included the New Statesman, Vanity Fair, Christie's, the Medical Foundation for the Care of Victims of Torture and Emily's List, a campaign to get more women into Parliament, but in 2002, Ms Macauley left the company to work part-time.
Ms Hobsbawm left the Polytechnic of Central London - now the University of Westminster - without a degree and got her first job in publishing.
In 1987, she joined Thames Television as a researcher for the programme Books By My Bedside, later becoming a researcher on BBC1's Wogan. She soon realised, however, that television was not for her and became a fundraiser for the Labour Party. Already bitten by the PR bug, after the 1992 general election she founded Julia Hobsbawm Associates in her living room.
The vivacious married mother of five became embroiled behind the scenes in the media furore which arose last year over the revelations of the former Home Secretary's affair with her best friend.
The pair are so close that when Mrs Quinn was pregnant with her first child in 2002, she wrote an article for the London Evening Standard newspaper explaining why she and not her husband, would be present at the birth.
In 2003, Ms Hobsbawm became Britain's first professor of public relations, setting up an degree course in PR at the London College of Printing.