Downing Street has declined to comment on remarks by Ken Livingstone that he longs for the day when the Saudi royal family are hanging from lamp-posts.
The mayor is no stranger to controversy
The London mayor, recently readmitted to the Labour Party, also attacked US policy towards the Middle East.
He blamed the plight of Palestinians on the "network of corruption" between some oil sheikdoms, oil companies and the White House.
Tory mayoral hopeful Steve Norris called the comments a "dangerous rant".
Lib Dem mayoral candidate Simon Hughes said Mr Livingstone's remarks about the Saudi royal family were "deeply unhelpful, offensive and inappropriate".
A spokesman for the Labour Party meanwhile referred enquiries to the mayor's office.
In his interview with the Guardian, Mr Livingstone also said people should put the terrorist threat to London into perspective.
"Terrorists will get through, they will take lives. But put it in the perspective that this year we will kill 300 people in road accidents in this city - and on that basis no-one would leave their homes in the morning," he said.
That prompted Mr Norris to issue a statement in which he accused Mr Livingstone of "incitement".
"With the threat of a terrorist attack on London in the air, this kind of Livingstone rant is downright dangerous," he said.
"This is exactly the kind of incitement that could have very serious
consequences for our country - and the Mayor does not give a damn."
A spokesman for the mayor then accused Mr Norris of trying to "whip up a fake fury".
"For the whole of his political career Ken Livingstone has been a forthright
politician who speaks his mind and Londoners have not so far found this a
problem - on the contrary, most people prefer to have someone in office who
doesn't always toe the line."
The mayor's alleged remarks about the Saudi royal family were quoted in full in the London Evening Standard.
It reported him as saying: "I just long for the day I wake up and find that the Saudi royal family are swinging from lamp-posts and they've got a proper government that represents the people of Saudi Arabia."
In his interview Mr Livingstone also said rejoining Labour earlier this year had boosted his access to decision makers.
Dump George Bush?
Left-winger Mr Livingstone was expelled by Labour when he ran against the party's London mayoral candidate Frank Dobson.
Now back in the fold, he is clearly not prepared to temper his remarks, calling for a 50% rate of tax for those earning over £100,000 a year- a key plank of Liberal Democrat policy.
Mr Hughes said: "Mr Livingstone has already adopted the Lib Dem idea of scrapping the Council Tax and replacing it with a local income tax, now he is in favour of the Lib Dem policy to implement a top rate 50% tax on the highest earners."
In his interview with the Guardian the mayor said: "Effectively, taxes have gone up under Labour and that has gone into extra funding for public services; and I think that people are seeing the improvements."
Describing his relationship with Mr Blair, Mr Livingstone said: "He's not going to make me foreign secretary and I'm not going to persuade him to dump George Bush.
"We work together on things we agree about and we accept there are going to be things we don't agree about."