Boris Johnson has spoken out in favour of immigration, hours ahead of David Cameron's much-anticipated speech on the subject.
The London mayor endorsed the expected announcement on benefit restrictions for out-of-work migrants but added "the last thing we should be is negative".
Speaking at a Chamber of Commerce lunch in Singapore as part of a regional tour, Mr Johnson insisted there should not be any sign of hostility to highly qualified working immigrants.
The mayor made a point during a question-and-answer session not to name Ukip, insisting the Eurosceptic party would quickly melt away as the SDP did in the 1980s.
Mr Johnson said: "I haven't had a chance to read in detail what the Prime Minister is saying today but I think he's on pretty much the right lines.
"What he's trying to do... our benefits system, which is very much more generous than those of many other EU member states, from acting as a suction force, a pull, to people who aren't wanting to come and work but to (pull) of the state or whatever.
"I think the numbers of such people are probably pretty small but there is unquestionably a phenomenon. There is no doubt people see our benefits system in the UK as an attraction for coming here.
"What David Cameron is proposing seems very sensible - you would have a four-year hiatus before you could get such benefits.
"But what would be a bad idea, for us in the UK, would be for the UK to send out a signal we are somehow hostile to talent and hostile to brilliant people who want to come and make their lives in our country - 40% of Londoners were born abroad. The dynamism of the London economy is intrinsically bound up with its ability to attract talent.
"The last thing we should be is negative."
On Ukip and their success in winning two MPs, Mr Johnson added: "It is not (unprecedented), there was something called the SDP - they disappeared like the puffball they were.
"I think that party, which I will not dignify by repeating the name, the party has no positive prospectus for this country whatever.
"When I look at the way things are stacking up I think it is highly unlikely it will be, they will come through in May 2015 with any more than a couple of seats.
"They won't change the political landscape except to make it more likely, alas, the leader of the Opposition would be in Downing Street - which would be a catastrophe."
In an extended section of his prepared speech, Mr Johnson discussed "alien" plants which had been introduced to Britain from abroad, including the English rose from Iran, garden peas from Turkey and London plane trees from Spain and Belgium.
He said seedlings from Kew Gardens, originally from Brazil, had been the foundation of Singapore's botanic garden. The mayor will visit the garden tomorrow with Kew executives to mark the relationship.
He said: "I tell you, there are people who would probably chop those trees down and send them back.
"Let us work to encourage the free trade between our countries, the exchange of ideas, the movement of talent, the great cross pollination and cross fertilisation that has advanced these two global entrepots since they were founded."
Earlier in the day, Mr Johnson had a 50-minute meeting with Singapore prime minister Lee Hsien Loong.
Theyr discussed a range of matters, including tax on foreign homebuyers, which is policy in Singapore, how to tackle population growth and terror threats.
Mr Johnson also attended a special event for financial technology companies at the Marina Bay Sands complex, witnessing a demonstration of new applications and giving a speech praising the value of the growing sector to the capital.
The mayor also took a brief ride on the city's underground, or MRT system, drawing a crowd of locals taking his picture.