Martin Amis’s mother and stepfather are under threat of losing their home in their adopted country of Spain after speaking out against a massive tourist development.

Spanish developers have filed a lawsuit seeking €22 million (£14.6 million) in damages from Lord and Lady Kilmarnock and two other expatriates, citing “slander, coercion, intimidation and threats” against them.

They blame the publicity campaign against the development for the number of investors who have recently pulled out of the €100-million Los Merinos scheme, which was to be built alongside the Sierra de las Nieves National Park near Ronda, where the Kilmarnocks have their home. The development plans included a double golf course, 800 houses and three luxury hotels.

Opponents say, however, that the drought-stricken area, a Unesco-protected heritage site, cannot support such a drain on its water supplies without seriously damaging the environment.

Lord Kilmarnock, 80, who has written several books about the area, has been a vociferous opponent of the scheme, speaking out against it repeatedly in the Spanish media.

Friends of the peer, who is unable to comment on the case for legal reasons, say that he is devastated by the suit, which he fears may bankrupt him and cost him his beloved Andalucian home.

The Kilmarnocks, Alastair Boyd and his wife, Hilly, have owned their home in Ronda for more than 20 years and have lived there full-time since the death in 1995 of Kingsley Amis, Lady Kilmarnock’s former husband. Before moving there they lived with the ailing Kingsley, a domestic arrangement devised by Martin.

Amis Jr has been a regular visitor to the house, which he used as a retreat to write his first novel, The Rachel Papers, published in 1973. He still visits his mother and stepfather there twice a year, most recently two months ago when the controversy over the development was at its peak.

The Spanish Green Party has leapt to the Kilmarnocks’ defence, demanding an investigation into the “mafia-style harassment” they have faced at the hands of the developers.

A friend of Lord Kilmarnock’s spoke of the stress that he was under. “Heis very anxious and concerned about losing his house. He would have taken this in his stride a decade ago, but he is now growing old and frail and it has hit him for six.

“It is particularly scandalous given how much he has done for the area over the past half century.”

The case is due to be heard in court next week.

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