The editor of the British Sunday Times newspaper, John Witherow, has been appointed acting editor of the Times despite opposition from the paper's independent directors.
The BBC reports Mr Witherow is understood to have been the choice of Rupert Murdoch, chairman of the Times's parent company, who is rumoured to want to merge both titles.
Mr Murdoch signed legal undertakings with Margaret Thatcher's government in 1981 that the Times and Sunday Times had to be kept separate. To protect editorial freedom, the appointment of the Times editor had to be approved by the paper's independent national directors.
Any move to merge the papers could mean waiving the legal undertakings.
Mr Witherow's formal appointment has been delayed amid disagreement over the possible merger of the two titles, a BBC correspondent says.
Talks between News International and the paper's independent directors are now effectively at a stand-off.
News International insists that it has not decided to take such a move and says it has "more immediate priorities" than a merger.
Mr Witherow has been editor of the Sunday Times for 18 years.