Downing Street has given its full backing to new MI6 chief John Scarlett.

The comments came as the Liberal Democrats called for Scarlett to step aside following the Iraq dossier row.

But a Number 10 spokesman said Tony Blair still supported the decision to appoint Scarlett to the top spy post.

The spokesman said the prime minister still believed it was a "very good idea" to appoint Scarlett.

Following the Iraq dossier controversy and criticism from the Butler inquiry, the Lib Dems said the public would not have confidence in the new spy chief.

Foreign affairs spokesman Sir Menzies Campbell said the new MI6 director general should stand aside.

"It seems to me that the controversy... is going to follow Mr Scarlett into this most important and significant appointment in which the public has to have confidence," he said.

The prime minister's spokesman also refused to deny a report that Scarlett asked the Iraq Survey Group to include 10 "golden nuggets" in its report on weapons of mass destruction, including a claim that Iraq had smallpox weapons or was trying to produce them.