The personnel commissioner, Erkki Liikanen, said he had received evidence that at least one question paper had been leaked before the test on Monday last week.

He said that to ensure equal treatment of all candidates everybody would now have to resit the exam.

The tests were held in 38 cities across the Union and cost more than $1m to organise.

Mr Liikanen's announcement came after the European Commission confirmed that its officials were investigating allegations of large-scale cheating in exams held in 38 different centres across the 15 European Union states.

Mobile phones and relatives

In Brussels, there are allegations that some candidates were able to leave the room to go to the toilet while the exam was in progress.

But once there, they are said to have used their mobile phones to check answers.

In Rome there has been one complaint to the police that some candidates had been given a preview of the multiple-choice test from relatives already working in the commission, the night before.

Chaos rules

But there are claims, too, of bureaucratic chaos.

In Milan, hundreds of potential future EU diplomats and lawyers were sent to the wrong address and were unable to sit the exam.

In Rome, there was a two-hour delay while officials hurried to make enough copies of exam papers, as different papers had been given to different candidates at the same time.

Privileged positions

Correspondents say that commission employees are among the most privileged civil servants anywhere in the world.

A secretary will typically earn twice the market rate in Belgium and pay less than half the tax.

The monthly gross salaries of middle managers average above $8,000 and employees are effectively guaranteed a job for life.

Correspondents say EU exams are no strangers to embarrassment surrounding the Euro-exams.