This is despite these residences being part of a $100 million clean-up program that took place between 1988 and 1993 and targeted roof cavities of houses with Mr Fluffy insulation in them.

Residents will receive a letter from Tuesday warning them that ''it is likely that some insulation material remains in these homes, including in places such as internal and external wall cavities, sub-floor spaces and underneath cornices.''

It is believed the warning follows disturbing findings of the extent of asbestos contamination in a home on Bradfield Street in Downer, which was accidentally missed during the Commonwealth's original removal program. Last July it was encased in a plastic bubble, pulled apart and buried in an asbestos dump at a cost to ACT taxpayers of more than $2 million.

ACT Work Safety Commissioner Mark McCabe, on behalf of the government, has written the letter, which strongly warns all homeowners against any renovation or even minor disturbance of their walls, sub-floors or eaves, until their homes have been inspected by a licensed asbestos assessor.

The cost of such an inspection will be about $700.

The loose amosite asbestos that was used as a cheap form of insulation installed in the 1960s and '70s by ''Mr Fluffy'' Dirk Jansen and his sons, is now known to be among the deadliest forms of asbestos as it is easily airborne and its minute particles are difficult to contain.

Mr McCabe said that while the Downer house was at an extreme end of the danger spectrum in that it had never had the original loose asbestos removed from its roof and it had been left to dissipate and deteriorate over two decades, it ''confirmed what we have always known, which is that there can still be material behind the walls''.

ACT Workplace Safety and Industrial Relations Minister Simon Corbell said homeowners had been reminded about asbestos safety in 1993 and 2005 but the government was now ''stepping up'' its ''proactive program''.

''People may think, 'well my home has been remediated as part of the program so there is no need for concern','' Mr Corbell said.

But it was critical in homes that had been exposed to Mr Fluffy that owners understood the risk.

''I am not interested in creating some sort of panic - that would be unjustified.

''These homes are not unliveable if they are managed,'' he said.

Meanwhile, he had instructed his directorate to strengthen the information made available to prospective buyers regarding a home's potential to contain remnant loose asbestos.

''There is already information on the title, and you can make further inquiries on the building file, which should be done as part of the conveyancing, but I have asked my officials on how we can strengthen further the information made available on the title - I think we can do more in terms of that advice and that work is ongoing.'' Mr Corbell said he was not in a position to speculate whether this information would potentially devalue a home when it came on the market.

He also noted that the ACT government was not liable for any further remediation of homes.

''The program was never represented as saying it would completely clean the property - it was always very clear it would clean the

most accessible part of the property but there was no guarantee or warranty on the remainder of the property,'' he said.

He blamed the ACT's asbestos contamination on ''inaction on the part of various federal governments prior to self government''.

''The ACT government will continue to pursue the federal government for contributions to the clean-up of asbestos and other contaminated materials that were dumped under their watch.''

A hotline has been set up through Canberra Connect on 13 22 81.