The opposition alleged that many people voted more than once
Moldova must set up an election inquiry that includes both opposition parties and international groups, says the EU's envoy, Czech PM Mirek Topolanek.
Moldova has set up an inquiry into the recent election and the riots that followed, but it is dominated by the ruling Communists.
Mr Topolanek met Communist Moldovan President Vladimir Voronin in the capital Chisinau on Wednesday.
He said both sides needed to show more will to engage in talks.
"For me, unfortunately, the will to start a dialogue exists only in verbal terms," Mr Topolanek said, adding that the EU was "ready to contribute to a resolution of the situation".
The result of a recount of election ballots announced on Tuesday confirmed that the governing Communist Party had won.
The election triggered riots in Chisinau this month, with opposition parties alleging vote-rigging.
Moldova blamed neighbouring Romania, an EU member, for stoking the violence and expelled the Romanian ambassador.
Mr Voronin met the EU delegation in a hotel in central Chisinau, because his offices, attacked by protesters two weeks ago, are surrounded by scaffolding.
Mr Topolanek's call for a broad inquiry commission is what opposition leaders have called for - they handed him evidence of what they said was 20,000 rigged ballots and a file with the photos of protesters whom they claim were badly beaten or even killed by the police.
Mr Topolanek's is the first high-level EU visit to Moldova since the riots.
The European Parliament is also considering whether to send a fact-finding mission and EU foreign ministers will debate the situation next week.
But behind the scenes, says the BBC's Europe correspondent Oana Lungescu, there is also concern about Romania's offer to speed up granting passports to up to a million Moldovans - a quarter of the country's population - which would give them access to the rest of the EU.
Most of Moldova was part of Romania until the Soviet Union annexed it in 1940, and there remain close cultural links between the people.
But it is hard to see how the passport offer would contribute to bolstering Moldova's stability, an EU diplomat said, and it will not gain Romania any sympathy in other EU countries.