An office building owned by an ethical company could soon become “the most unethical set of flats”.

That’s according to Waterlow Road residents in Archway, who have said the planned eight studio flats, of 13.5-17sq m, would be smaller than a child’s bedroom.

The building, at 1A Waterlow Road, is owned by Ethical Property, a foundation that campaigns to reduce social and economic impact of commercial property.

But it has agreed to sell the office space, home of the Green Party until 2012, to Foley Building Contracts, which will build the flats.

Nearby resident Natasha Jackson said: “This is the most unethical type of development you can have.”

Now, Waterlow Road residents are urging the company not to go ahead with the sale to prevent the flats from being built.

Ms Jackson, 45, said: “Those flats would be smaller than my child’s bedroom.

“It is completely irresponsible planning. We don’t want people living in these terrible cramped conditions.

“They would be isolating and shouldn’t be allowed, yet developers can just get around it.”

Ms Jackson pointed out she was not angry at Ethical Property, but said it should now abide by its core commitment that every decision it makes will “take account of environmental and social impacts”.

She said: “Ethical Property sold the building in good faith, on the basis of a two-flat conversion and not what is proposed.

“It seems to be a really good company and has been in the street for a long time as owners of the building.

“I believe it has the best intentions and hopefully we can persuade it to hold the plans, or otherwise develop the building to good standards and then sell it.”

Under Islington Council rules, flats need to be a minimum 37 sq m. However, even though eight flats are under half the required size, the plans will be given automatic approval under rights introduced by the government in 2013.

The rights, known as permitted development, mean that buildings being converted from office to residential use do not need planning permission.

Ethical Property has so far been unable to comment.