A planned biography of Rupert Murdoch last night appeared to be the first victim of the takeover by his HarperCollins publishing company of its small but highly regarded rival, Fourth Estate.

The unauthorised book by Michael Crick on the Australian born media owner promised to shed light on the apparently unstoppable rise of Mr Murdoch - but will now not be published by the British company.

Mr Crick, best known for unearthing John Major's first love and tracing the long lost relatives of Lord Archer, received a six figure advance last year for the Murdoch book.

Mr Crick was unavailable for comment last night. But his wife - and his sometime researcher - said: "Both sides [Fourth Estate and Mr Crick] have agreed he cannot do the book and his agent is trying to reach some kind of settlement."

The takeover has sent shivers through Fourth Estate staff who remember the furore at HarperCollins over a planned book about Hong Kong by former governor Chris Patten. The book was dropped amid allegations that Mr Murdoch had personally forced HarperCollins to do so because it was critical of China, where the media baron was keen to do business. Victoria Barnsley, the founder of the London based independent Fourth Estate, yesterday sold the company for an estimated £12m to the US based group. She has been appointed chief executive of HarperCollins UK.

She dismissed the political implications of Mr Murdoch being the new owner and insisted no definite decision had been made on whether or not to go ahead with Mr Crick's book.

"I have spoken to Michael and I will be speaking to his agent again," she said. "It is difficult for him and we recognise there is a general conflict of interest."

The 36 staff at Fourth Estate are expected to move to HarperCollins' London base in Hammersmith. No significant redundancies are expected although Ms Barnsley refused to rule out job losses.

Fourth Estate was launched in 1984 and quickly built up an impressive reputation, bringing award winning authors such as Annie Proulx and Dava Sobel to a wider UK audience.

HarperCollins would not say how much it had paid for Fourth Estate, whose biggest shareholder was the Guardian Media Group, publisher of the Guardian newspaper. But well placed sources confirmed the £12m figure and said Ms Barnsley held around a quarter of the shares.

The Fourth Estate founder said she was not motivated by personal financial gain. The decision to sell was taken unanimously by the executive directors.

HarperCollins was the most attractive of a number of offers. It was important that HarperCollins offered a big step into the US market, where Fourth Estate has no presence.