The news marks a turnaround on the issue as earlier this year the committee of citizen's freedom and rights, justice and home affairs backed a proposal allowing companies to spam people -- provided there was an opt-out option for recipients.
The decision was expected to be finalised but MEPs today voted for forcing companies to gain consumers' approval before sending unsolicited emails.
But there will be no immediate decision on the issue as MEPs, concerned over the number of amendments made to the bill, voted to send it back to committee.
At the moment many online agencies send out junk email messages from advertisers who have registered with unrelated websites.
If the directive is finalised, advertisers would only be able to spam users who had checked a box requesting information from third parties.
A decision is expected towards the end of the year.