Speaking at the CML conference Sheila Nicoll, director of conduct policy at the FSA, said although buy-to-let regulation was a "matter for government" to decide the FSA had considered its implications.
She said: "We certainly see the logic in having buy-to-let regulated alongside the residential mortgage market."
As it stands buy-to-let mortgages against residential properties will be caught by European regulation currently being debated in Brussels.
The Association of Mortgage Intermediaries said last month that buy-to-let regulation was already "a done deal" and all that remained was to thrash out how the practicalities.
The Intermediary Mortgage Lenders Association meanwhile said the debate was still in play.
