John Witherow is appointed new editor of the Times

The editor of the Sunday Times, John Witherow, has been appointed acting editor of the Times, despite opposition from the paper's independent directors.

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.

Such a move could mean waiving legal undertakings Mr Murdoch signed in 1981 to keep the titles separate.

News International says it has "more immediate priorities" than a merger.

The deputy editor of the Sunday Times, Martin Ivens, has been made its acting editor.

The previous editor of the Times, James Harding, stepped down last month. He said it had been made clear to him that the publishers wanted to appoint a new editor.

Since then Mr Witherow, who has been editor of the Sunday Times for 18 years, has been seen as the most likely successor. But his formal appointment has been delayed amid disagreement over the possible merger of the two titles.

Talks between News International and the paper's independent directors are now effectively at a stand-off.

Mr Murdoch signed legal undertakings with Margaret Thatcher's government 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.

But other newspaper groups - such as the Telegraph - are now moving to seven day working, to cope with tougher financial conditions in the industry and the practicalities of publishing on the internet.

I understand that News International has taken informal advice from the Department of Culture Media and Sport, over whether the government might allow the undertakings to be lifted, and if so how that might be achieved. But the company insists that it has not decided to take such a move and has more immediate priorities.

Two weeks ago, a new chief executive, Mike Darcey, arrived at News International and in a statement issued on Friday night, he said that Mr Witherow would take over at the Times "effective immediately, subject to formal approval as editor by the independent directors" of Times Newspapers Ltd.

Mr Darcey said consultation would continue with the independent directors over the undertakings given in 1981.

"Following a meeting of the Independent National Directors of the Times and the Sunday Times yesterday we welcome their clear understanding of the very difficult financial position of our newspapers and therefore the need to address the undertakings given in 1981," he said.

"A thorough assessment of the undertakings will enable them to make recommendations to us and to government as to how the newspapers can be structured in order to reduce their costs and become economically viable.

"However, during this interim period of continued consultation over the undertakings, we still have a responsibility to provide these two newspapers and their journalists with strong and stable leadership."

The six independent directors of the Times include Veronica Wadley, a former editor of the London Evening Standard; Rupert Pennant-Rea, a former editor of the Economist and deputy governor of the Bank of England; and Stephen Grabiner, a venture capitalist who previously held senior commercial posts at the Daily Telegraph and the Daily Express.

There is now effectively a stand-off between these directors and the News International management, who had expected Mr Witherow's appointment to be formally approved at the meeting.

The independent directors have demonstrated their independence but despite Mr Darcey's statement it is not clear whether they believe the papers' "very difficult financial situation" could justify the changing of the undertakings. He has now challenged them to recommend how they think the papers can be made economically viable.