Steve Quartermain, chief planner at the Department for Communities and Local Government (DCLG), said that 19,000 homes had come forward already, including 6,000 in London,
He was speaking about how planning can enable economic growth at the Institute of Economic Development (IED) Annual Conference in London yesterday.
In May last year, the government introduced new permitted development (PD) rights easing office-to-residential conversions for a three-year period.
Quartermain said the number of homes that had come forward as a result, revealed in a submission during a recent consultation, was "significant".
He said: "One of the bits of evidence that we have had is the indication of the number of units that are coming through as a result of this permitted developmen right - and it's significant.
"It's 6,000 in London, 19,000 across the country, and 32,000 is predicted."
In an impact statement published when the policy was introduced, the DCLG estimated that between 90 and 180 office-to-residential changes of use, excluding areas that are exempt from the changes, to take place each year.
A report published earlier this month by property consultancy Jones Lang LaSalle found that just 10 schemes were "either under construction or have been delivered so far in London" as a result of the changes, but expected that "over 10,000 units may be delivered across the UK".
The move has caused anger among some local authorities, particularly in London, who worry about losing employment space and jobs.
In July, the DCLG consulted on extending residential PD rights further, including allowing the conversion of warehouses and light industrial buildings.
It also proposed making the temporary office to residential PD rights permanent and removing the current exemptions in specific areas, such as central London.
Quartermain said the government was "considering" the responses it received during the consultation and said it would take on board criticism.
He said: "We've had challenges on the economic impact and standard of conversions.
"Some people are saying some of the conversions are quite low standard, they are too small and too cramped.
"But it's something that the market needs and how people want to live.
"That's a balance we need to strike and get right. We are looking at that."
Defending the introduction of the PD rights, he said: "The government's intention was very clear. They said: 'We have a housing crisis and there's an opportunity for existing buildings in the urban fabric to make a contribution to housing supply.'"
Some applicants achieving prior approval were not actually carrying out the conversions, Quartermain said, but selling on the property once permission had been achieved.
He went on to say that authorities could use Article 4 directions or draw up policies in their local plans to protect certain areas from the impact of the PD rights.
The IED Annual Conference was staged in association with Planning and Placemaking Resource. It was sponsored by Nathaniel Lichfield & Partners, Grant Thornton, YKTO Group, Tractivity and WECD.