Safeguards introduced to combat electoral fraud "are easily bypassed" because of weaknesses in the voter registration system, it was claimed.
Sir Christopher says changes to the electoral system are needed
Standards chief Sir Christopher Kelly, said household registration could not stop bogus names being registered and used as fraudulent postal votes.
The Electoral Commission says it wants individual voter registration.
A Tory councillor was found guilty of using bogus postal votes to ensure he was voted into office in Slough.
Eshaq Khan beat Lydia Simmons, a former mayor of Slough, by 119 votes to win the council's Central ward in last year's local elections.
But a special election High Court, in Slough, convicted Khan and his agents of corrupt and illegal practices.
They are related to applications for registering to vote and postal voting. He was banned from standing again and a by-election will now be called in the borough.
Khan has also been expelled from the Conservative Party.
He and his electoral team were found to have created hundreds of false names in the weeks running up to the 3 May election and entered them on the electoral register for the ward, the court heard.
They then made applications for postal votes for these "ghost voters" and used the ballots to vote for Khan.
It was only when Labour party activists, surprised by the Conservative victory in an election which had otherwise been a success for Labour, pressed for an investigation that the fraud was discovered, the hearing was told.
'Affront' to democracy
Election commissioner Mr Richard Mawry QC said: "The only reasons they came to light at all were the incompetence of the fraudsters and the blatant nature of the frauds.
"It would have been pleasant to conclude this judgment by saying that this had now all changed.
"But I cannot. Despite the 2006 Act, the opportunities for easy and effective electoral fraud remain substantially as they were on 4 April, 2005."
Individuals take personal responsibility for registering
The register reflects more accurately who is entitled to be registered
Greater accuracy helps restore integrity to the registration process
Helps minimise electoral fraud
Sir Christopher, chairman of the Committee on Standards in Public Life, said the Slough fraud "highlights the need for fundamental changes to our electoral system".
"Electoral fraud is not a trivial matter - it is an affront to the democratic principle of one person one vote," he said.
"Left unchecked it will eventually undermine trust and confidence in the democratic process and by implication the electorate's consent to the outcome of elections.
"This case has shown that the safeguards introduced by the government to combat electoral fraud particularly in relation to postal voting are easily bypassed because of the fundamental weaknesses in the current system of electoral registration."
Sir Christopher has called for the government and other main political parties to agree to introduce a system of individual registration after the next general election - similar to one already in place in Northern Ireland.
Sam Younger, chairman of the Electoral Commission, said the electoral system would continue to be "open to abuse" until the voter registration system is changed.
He said it was "not realistic" to take postal votes away from voters if they want to use them.
"We should make sure the integrity of the system is there with individual voter registration," he said.