The Government is expected to order a clampdown on special advisers "spinning" the media as the row continues over Jo Moore's conduct.

There have been growing calls for Ms Moore, special adviser to Transport Secretary Stephen Byers, to be sacked after she sent an e-mail on 11 September urging colleagues to use the news fallout from US terror attacks to "bury" bad news.

Several Labour MPs were among those calling for her resignation.

But Mr Byers has stood by his aide, saying that while she had made "a terrible error of judgment" it was "an isolated mistake."

Sacking inappropriate

Indeed he said it would been "inappropriate" to sack her on that basis.

The memo was written after both towers at the World Trade Center had been attacked but before they collapsed.

There were also allegations, which have been denied, that Ms Moore put pressure on civil servants to brief against London Underground boss Bob Kiley.

Downing Street is now expected to stress to special advisers that they should concentrate not on spinning stories to the media, but rather on advising ministers about the political implications of their decisions.

They will also be reminded that they must not do anything which would compromise the political impartiality of civil servants.