Martin Newland resigned as the editor of The Daily Telegraph this morning after a leader column he commissioned backing David Cameron for the Conservative Party leadership ended up on the newsroom spike.

That episode was the last in a string of developments at the newspaper interpreted by staff as management interference in editorial decisions.

The pro-Cameron editorial was written on Friday last week, Telegraph sources say. The decision to drop the editorial, which had been prepared for publication, is understood to have been taken on the orders of Murdoch MacLennan, the chief executive of the Telegraph Group.

Telegraph leader writers had spent a long time considering who to back in the race between Mr Cameron and David Davis. But, as Mr Cameron moved clearly into the lead, Newland thought it was time to back the younger candidate. The endorsement of the Conservative-supporting Telegraph is usually considered critical in any race for the party's leadership.

Towards the end of the day, however, that decision was suddenly reversed, amid suggestions that more time was required to consider the merits of both candidates. It is not clear what process led to Mr MacLennan halting the editorial.

Staff at the broadsheet newspaper believed that the decision had been taken following consultation with the Barclay family. The newspaper is owned by Sir David and Sir Frederick Barclay, and its immediate holding company is chaired by Sir David's son Aidan Barclay. However, earlier this week, Sir David Barclay asked The Guardian to point out "neither he nor his brother Frederick intervened in The Daily Telegraph's deliberations".

At the same time, Newland was embroiled in a dispute following the decision of Mr MacLennan to install veteran journalist John Bryant from the Daily Mail as Editor-in-Chief of both the daily and Sunday titles.

The move was the most high-profile in a series of recent senior appointments about which Newland, 44, was apparently kept largely in the dark. He is believed to have felt "undermined" that Bryant had been brought in above his head.

Bryant, 61, will replace Newland as acting editor until a replacement is found. The obvious internal candidates comprise recent arrivals Jeff Randall, editor-at-large, Simon Heffer, associate editor and Will Lewis, one of two deputy editors. Sarah Sands, who has only recently moved to the Sunday Telegraph editorship, and Neil Darbyshire, another deputy editor, would be on the list, and Bryant may also want to be considered.

Addressing Telegraph staff this afternoon, Bryant told them that he will be in charge for "a few months". He is understood to have said that he will "slow down" the pace of change, and was critical of the state of the newspaper. He did not give a direct response when asked if he would be able to decide if the editor of The Telegraph would have the power to back David Cameron, Telegraph sources report.

Sources at the newspaper say that Bryant, a well-regarded news journalist who is a former deputy editor of The Times, could remain at the helm of the broadsheet for a year or even longer if his tenure is deemed to be a success.

Newland was appointed Telegraph editor by Conrad Black in October, 2003. He had barely had time to get his feet under the table when the Canadian press baron was forced to step down from the board following accusations of fraud in the United States and Canada two months later. Black denies these accusations.

Hollinger's directors put the Telegraph up for sale, leading to months of uncertainty before an eventual purchase by the Barclay brothers in June last year.

Newland survived the ensuing cull, which saw Dominic Lawson, the editor of the Sunday title replaced by Sands, then Newland's deputy. There was also a series of 300 editorial job cuts which sapped morale as the newspaper was perceived to be shifting downmarket.

A re-design, which saw the paper divided into three sections, launched last month. But it was followed by a fall of 0.29 per cent in overall circulation.

Newland will leave at the end of the month and staff were officially informed of his departure by the outgoing editor this morning. It is not clear if he will receive a pay-off.

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