Aviva Plc, the UK insurer and asset manager, warned the government that new safety proposals for high-rise apartment blocks could steer institutional investors away from the residential property market.

The company last year urged the government to consider how its Building Safety Bill, which addresses long-standing concerns around the development and management of homes, would financially impact their owners, according to an excerpt of a letter dated Nov. 20 and seen by Bloomberg News. Aviva manages a large portfolio of residential blocks on behalf of its investors.

The legislation was published last week and is expected to take at least nine months to pass into law. The plans to overhaul regulations will cost the building industry 731 million pounds ($1 billion) in the first two years, and then 283.7 million pounds annually, the government estimates.

The reforms could potentially make “it unviable for institutional investors to remain in the residential property market,” Aviva’s former UK and Ireland General Insurance Chief Executive Officer Colm Holmes wrote in the letter to Building Safety Minister Stephen Greenhalgh. “This would have further unintended consequences for U.K. pension savers and leaseholders, and deprive leaseholders of the benefits of an institutional landlord.”

UK institutions are investing more in the lucrative rental housing market at a controversial time. Aviva’s warning adds to a raging debate about who should bear the billions of pounds of costs needed to fix unsafe buildings in the wake of the Grenfell Tower tragedy in 2017. Some 72 people were killed when the residential block, which had a number of safety defects, caught on fire.

Aviva’s asset management business, Aviva Investors, manages a fund that owns more than 1,000 high-rise residential blocks across England and Wales, according to an April company statement. The firm said that it was engaging with government on remediation issues in the wake of Grenfell, and was also investigating whether developers and contractors might be liable for costs.

“We support the principles which underpin the recently published Building Safety Bill,” a spokesperson for Aviva said in a statement on Monday. “This will have a wide range of implications for freeholders and we are currently examining the details to understand the extent and range of its impact on these groups, who we act on behalf of.”

The government’s proposals are aimed at increasing accountability across the sector and making homes safer. However, uncertainty still remains as to who will pay for defects in existing properties: homebuilders, property owners, leaseholders or taxpayers.

Overall costs for repairing unsafe buildings could eventually rise to 15 billion pounds, lawmakers estimated last year.

Top photograph: Grenfell Tower in North Kensington, London. Photo credit: Hollie Adams/Bloomberg.