· Row over Italian PM's plan to double size of villa · Council says cash fee will be used for town's benefit

With its imposing tree-lined drive, extensive outbuildings, surrounding park and 10,000-volume library, the neo-classical Villa San Martino appears to have everything the most demanding of tycoons requires of a home. And that is without the mausoleum - complete with giant, pink marble sarcophagus - that its owner, Silvio Berlusconi, has created in the grounds.

But some people, it seems, are never satisfied. Italy's billionaire prime minister wants to double the size of the property. And his plans are running into controversy in Arcore and beyond.

An opposition senator has tabled a question in parliament for Berlusconi's environment minister on the go-ahead for a project that would enlarge the government leader's mansion by more than half the size of a Serie A football pitch. Opponents claim that the scheme was modified, extended, and then rushed through a council controlled by his followers.

It is not the first time Berlusconi has come under attack for allegedly playing fast and loose with planning laws. Four years ago, he was accused of embarking on a grandiose embellishment of his seaside Sardinian estate without planning permission.

The project included the creation of an underground landing stage reminiscent of a Bond film. When a prosecutor attempted to investigate the objections, he found all Berlusconi's properties were covered by an official secrecy decree issued by Berlusconi's own government.

Dating from the 18th century, the Villa San Martino was bought by Berlusconi in 1974 with shares he eventually reacquired for just £100,000.

Some of the most important meetings of his turbulent political career have been held within its finely decorated walls, and it was at Villa San Martino in 1994 that he famously recorded a video announcing his entry into politics.

According to Fausto Perego, who was deputy mayor in the previous, centre-left council in Arcore, Berlusconi first applied for a relatively modest, 1,500-square-metre extension. This allowed for a gallery for his extensive collection of paintings, a museum for the Berlusconi-owned Mondadori publishing house and premises for a new foundation to be named after his father, Luigi.

The original scheme, Perego told the daily La Stampa, also included "the relinquishing of part of the property" so it could be used for the creation of a new square and a civic library to be designed by one of Milan's leading architect. But after the right took office in Arcore the project was changed.

Under the new arrangements, endorsed by the incoming council, the total size of the extensions was tripled. In place of land, the local authority will now get a cash payment of €600,000 (£470,000) in addition to €1.2m in extra planning levies.

"It's a tidy sum that we shall use for the good of all," said the mayor, Marco Rocchini. "I don't understand the opposition. There has been criticism of the speed with which we gave the OK. But everything was in order. What else were we meant to do?"

La Stampa quoted council sources as saying Berlusconi was ready to increase his contribution by funding an old people's home.

The 3,000 square metres in the revised plan are for an imposing four-sided building around a courtyard which, the newspaper speculated, could be used for short visits by the 71-year-old billionaire's children and growing numbers of grandchildren.