Mayor Sadiq Khan argues that people living in the capital should not be embarrassed about saying "first dibs for Londoners" when it comes to housing.
The London mayor was asked by ITV's political editor Robert Peston about why he has joined a campaign that criticised foreigners who bought expensive properties in London, but did not live in them.
Speaking on the Peston on Sunday programme, Mr Khan was asked if there was anything the mayor could do about them.
He added: "We could have for example a condition for permission to build homes is you must mark them for the first six months in London.
"I have got nothing against luxury properties being built in London. What we can't have is London being the world's capital for money laundering."