Housing director Rosanna Law said an iconic rainbow wall of Choi Hung Estate will have to be demolished, but officials will seriously look at restoring the spot after redevelopment.

Officials plan on moving the first batch of affected tenants to an estate in Kowloon City as early as four years from now, as an estimated 15 years will be needed to complete the phased renewal of the estate.

Speaking to RTHK, Law said the "rainbow" block of Tan Fung House and the sports courts next to it, which is above a multi-storey car park, would have to go.

"If we say we retain the rainbow wall and the car park, not only will we have fewer flats in the redeveloped estate, but I think it would be rather difficult in terms of having enough space, to improve the traffic conditions nearby," she said.

"But we understand how the public loves this photo spot. Our team of architects will seriously think about ways of restoring this 'rainbow' at the new Choi Hung Estate."

Law said authorities made the redevelopment announcement early, so that tenants can be psychologically prepared about having to move out and take part in the process.

She said if they don't want to move to Kowloon City and stay nearby, officials will try to accommodate if there are suitable flats available.

Law stressed that the second and third phase of the redevelopment - due to begin around 2035 - are still in a conceptual stage.

She explained the new blocks were meant to be up to 50-storeys high and officials cannot conduct works such as exploring the ground's foundation until after tenants have moved out.

Chief Executive John Lee also announced in his Policy Address last month plans to regulate sub-divided flats while requiring landlords to turn them into "basic housing units".

Law said it is illegal for landlords to break existing rental contracts early and force out tenants in the name of renovating the flats and she said tenants can report this to the authorities.

"In fact, the government has yet to set the standards [for basic housing units]. We haven't completed our public consultation and enact new laws. Do landlords have to rush to [renovate]?" the director of housing said.

"I appeal to the landlords, even if you're eager to make sure your flats comply with the new standards, you really should wait a little bit until we have promulgated the new standards. Otherwise you may waste your money."

Law said around 40 percent of tenants currently living in the potentially affected sub-divided flats, or around 40,000 households, should be ineligible to apply for public housing.

Authorities, she said, will not conduct large-scale law enforcement in future unless officials are confident they can find re-settlements for affected residents.