Bought for $10.5 million, the 314 sq m apartment at the Eden Residences Capitol Singapore, opposite St Andrew's Cathedral, is one of the priciest units in the Singapore property scene.

But Russian magnate Sergey Vbornov, 59, the former chief of Russia's largest diamond producer, wants out from the 2013 deal for the unit.

Mr Vbornov, who holds dual citizenship of Russia and St Kitts-Nevis in the Caribbean, is suing vendor Capitol Residential Development in the High Court for the return of monies paid to date amounting to some $8.89 million in sale price, stamp duties costing $1.88 million and $6,857 in conveyancing fees.

The more than $10 million claim makes it one of the largest lawsuits over housing defects here. The case is also noteworthy as Mr Vbornov is seeking a full refund, instead of compensation to make repairs.

Mr Vbornov, who collected the keys to his apartment on Oct 31 last year, alleged in court documents that the unit is "unfit for habitation and does not comply with the promised luxury standard", nor did it live up to the idea of "paradise found", as allegedly marketed.

Capitol Residential Development, defended by lawyers from Allen & Gledhill, are contesting the claims - pointing out, among other things, that the unit was not sold under the agreement as a "luxurious apartment" and/or "paradise found".

Court documents also show that Mr Vbornov hired inspectors who reported "numerous defects".

The claim papers filed by his lawyers from Infinitus Law Corporation list some 20 pages outlining the purported defects such as "poor finishing" in the living area. He claims the "unit has not been constructed to a high standard or to a reasonable standard" and attempts to rectify the issues have failed, given the inherent nature of the defects.

He added he is unable to rent out the unit for up to $25,000 a month because of its alleged condition.

In its defence, Capitol counters that it carried out works to the unit between March and October last year to address his feedback on the alleged defects. He had inspected the unit in March last year and complained about the alleged defects then. It stressed the works were conducted out of goodwill and without admission of liability.

Capitol pointed out that since handing over the unit in October last year to the owner, it has been unable to access the unit to verify the alleged defects or carry out rectification works.

Capitol further denied that any part of the unit's construction was unacceptable in terms of "operation, longevity, appearance, construction, weather tightness, safety, present and potential failure and lifespan, as alleged".

A High Court pre-trial conference was held this month, and the case is expected to go to trial next year.

Mr Vbornov also worked for the Foreign Ministry of the former Soviet Union. He was president of partially state-owned diamond producer Alrosa from 2007 to 2009.

•Additional reporting by Toh Wen Li