London Mayor Ken Livingstone has declared that rival Boris Johnson was the most formidable opponent he would face in his political career.
Mr Livingstone dubbed the Tory MP "a charming and engaging rogue" and predicted he would be "no walkover".
Mr Johnson - who is yet to be formally adopted by the Conservatives as their candidate - saw his bid to become Mayor boosted on Wednesday by an unofficial opinion poll suggesting he is in the lead among the capital's voters.
A small sample of London voters in a YouGov survey of voting intentions gave Mr Johnson a six-point lead over the Labour incumbent.
Speaking on BBC Radio 4's Today programme on Thursday, Mr Livingstone said: "My job in the next eight months or so is to get to focus on what Boris actually believes in.
"He has been writing three columns a week for 20 years. I am halfway through them."
And he added: "This man is to the right of Norman Tebbit - he makes Norman Tebbit look like a cuddly liberal.
"So I want to get on to the policy. This is not a sort of Celebrity Big Mayor. It's a serious issue about how you run the city.
"I am going to enjoy it, but know a lot of people say Boris will be a walkover. I think Boris is the most formidable opponent I will face in my political career - he's got a high profile, he is a charming and engaging rogue.
"That's why I want to get on to what he actually believes in and what he will do rather than whether you would want him as your next door neighbour."
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