Nastase is running for president in the November 28 poll

Mr Tiriac, who heads Romania's Olympic Committee, vowed to give away the car should the prime minister back up a 2001 pledge to build 400 sports halls.

Four hundred and two sports halls had been built, the ex-sports star said.

But critics say the bet was void, as some halls were still under construction or unusable.

A team of reporters from sports daily Gazepa Sporturilor visited Mr Nastase's home village of Cornu - where the prime minister has a farm - and discovered the only evidence of construction of a new sports hall was the laying of foundations.

We have to convince our leaders that sports is as important as mathematics or chemistry, and having only PhD's who can't run is not normal Ion Tiriac

Similar investigations have led some to accuse Mr Nastase - who is locked in a tight election campaign for the Romanian presidency - of using the bet as a political stunt.

However, Mr Nastase said the wager "benefited Romania's children" and has promised to sell the car in a public auction with proceeds going towards furnishing and equipping sports facilities.

In a small ceremony on Thursday, Mr Tiriac gave Mr Nastase the keys to a gleaming black Mercedes S500, saying it was a bet he was "happy to lose".

Romanians go to the polls on 28 November to elect a president.