Just two dozen or so MPs took part in the vote – which was held without a debate on the evening of June 28 - while the rest of the country was watching the crunch Euro 2012 football match against Italy.
German opposition parties vowed on Monday to block it in the upper house of parliament, the Bundesrat – and after extensive outrage was voiced across the country, the government is also backing off.
Government spokesman Steffen Seibert said on Monday that although the government had no influence over the rest of the parliamentary process, it was to be hoped that changes would be made before it passed into law.
The new registration rules enable local authorities that collate names and addresses to sell that information without asking.
Even if a person has said in writing they do not want this to happen, an information firm can update information they already have – to include a change of address, for example.
The reform was passed by the lower house of parliament, the Bundestag, in less than a minute. But it still needs to pass the upper house, the Bundesrat, where Merkel's coalition does not have a majority, to become law.
Federal Data Protection Commissioner Peter Schaar has called for the new registration law to be ditched in favour of the current one, which requires a citizen to give explicit permission for a local authority to give their information to a third party.
“It is not acceptable that data that the state makes a person give up is given to a third party for money, without the permission of the person concerned,” he said.
"What is clear is that this intention - as it was decided by the Bundestag - is a gift for the advertising industry," he added, speaking to Deutschlandfunk radio on Monday.
“The dissemination of data without the citizen having the option to prevent it, will not be supported,” said Peter Friedrich, Social Democratic Party (SPD) Bundesrat member.
He told Monday's Südwest Presse newspaper that every citizen should retain the ability to prevent the trade in their personal information.
“I do not believe that the law will survive the Bundesrat unchanged,” said Jens Böhrnsen, SPD head of Bremen state told the Neue Osnabrücker Zeitung on Monday.
As the opposition parties declared their intention to block the reformed law in the Bundesrat when it reaches there this autumn, even members of the government voiced criticism, with Consumer Minister Ilse Aigner calling for discussion. She told the Berliner Zeitung newspaper she felt the original veto to be the best way.
The law was due to come into force in 2014 as part of a general federalism reform, taking the responsibility for registration from the states to the federal government.