Mr Kolesnikov has called on President Medvedev to investigate his controversial claim. "A palace is being built on the Black Sea coast for the personal use of the Russian prime minister," Mr Kolesnikov wrote in his original letter. "As things stand, the cost of the palace is $1 billion. The funds were mostly raised through a combination of corruption, bribery and theft," he said. It was in President Medvedev's powers, he added, to show ordinary Russians that everyone was equal before the law including Mr Putin. Mr Putin's spokesman has dismissed the allegation out of hand however, as has Mr Kozhin, the Kremlin official whose signature allegedly appeared on the original contract. President Medvedev has not responded to the allegations either, at least not publicly.