Patience Wheatcroft, editor of the Sunday Telegraph newspaper, has resigned 18 months into her role, the third change in editor at the UK title in two years.

The Telegraph Group said Wheatcroft resigned on Tuesday, adding that sister paper the Daily Telegraph's deputy editor, Ian MacGregor, has been appointed to succeed her.

The Daily Telegraph's editor Will Lewis has been made editor-in-chief across the daily and Sunday Telegraph titles.

The Telegraph Group gave no reason for Wheatcroft's departure. Her predecessor was Sarah Sands who took on the role in June, 2005, after Dominic Lawson resigned.

Wheatcroft's exit comes a year after Telegraph reporters and production staff moved to a new multi-media newsroom in offices at Victoria, central London.

Unconfirmed newspaper reports on Wednesday said Wheatcroft left amid differences in opinion over the editorial direction of the paper.

The Sunday Telegraph, which relaunched with a new look in June, had a circulation of 636,681 in July, according to figures from the UK Audit Bureau of Circulation, making it Britain's second-biggest broadsheet Sunday behind the Sunday Times.

The Daily Telegraph is the biggest-selling national morning 'quality' UK newspaper, according to ABC figures, although its circulation of just over 889,000 in July was well below the 3.1 million achieved by the Sun, Britain's biggest-selling 'tabloid' daily which is ultimately owned by Rupert Murdoch's News Corp.

News Corp also owns the Sunday Times.

The Telegraph, named after the 19th century's newest technological innovation, is owned by the billionaire Barclay brothers who paid 665 million pounds ($1.3 billion) for the group in 2004.