The artificial sweetener aspartame is not linked to cancer, according to a report just released by the European Food Safety Authority (EFSA).
The European food watchdog undertook an urgent review of the additive following a study, published in 2005, which suggested aspartame was carcinogenic.
But a working party said the incidence of tumours could not be linked to the artificial sweetener.
It says there is no reason to revise the current recommended intake levels.
The review had been prompted by research undertaken by the European Ramazzini Foundation of Oncology and Environmental Sciences (ERF) in Bologna, Italy, which looked at the incidence of tumours found in rats that had been given varying levels of aspartame.
The study monitored more than 1,800 rats, following them throughout their lives.
The results, the foundation believed, showed that aspartame had the ability to induce cancers in a number of sites in the animals' bodies.
Following the publication of the study in the European Journal of Clinical Oncology, the EFSA ordered a review of the safety of the sweetener.
An EFSA sub-group, the Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (AFC), put together a working party of European food experts to analyse the foundation's study and to look at other research involving aspartame.
Although AFC said ERF's study was "very extensive", the working group disagreed with the conclusions it had come to.
Dr Iona Pratt, chair of AFC's working group, said: "The Ramazinni Foundation's study showed an increase of cancers of the blood - lymphoma and leukaemia - in the rats."
But, she said, the working group concluded that these tumours were not related to aspartame.
AFC said the rate of the tumours was not related to the dose of aspartame, which would have been expected if there was a link.
The working group believes that a respiratory disease, found in many of the rats that took part in the study, was the likely cause of the tumours.
The AFC also looked at the incidence of kidney tumours and changes to the kidney believed to have been caused by aspartame, but concluded this was an outcome specific to rats.
It also said the diagnoses of some of the cases of malignant schwannomas (a rare type of tumour) had not been confirmed by other scientific institutions, and that the sweetener showed no evidence of genotoxity - the ability to damage DNA.
"On the basis of the evidence," said Dr Pratt, "there is no reason to revise the previously established Acceptable Daily Intake (ADI) or to undertake any further revisions of the safety of aspartame."
The ADI is the level of additive considered to be safe if consumed every day over a lifetime without risk to health.
For aspartame, the ADI is set by the European Commission's Scientific Committee on Food (SCF) at 40 milligrams per kilogram of body weight.
An adult would have to drink about 14 cans a day of diet soft drink, or consume about 80 sachets of sweetener to reach this amount.
A spokesperson from the UK's Food Standards Agency said: "The EFSA's announcement raises similar concerns about the Ramazzini study to those expressed by the UK's independent expert group, the Committee On Carcinogenicity (COC), earlier this year.
"The COC identified a number of issues that indicated the results of the study may not be reliable. These related to concerns about the health status of the animals, some details of methodology which do not conform to currently accepted best practice and adequacy of external peer review."
But ERF stood by its study and said in a statement: "Because of the globalisation of the industrialised diet and the ever increasing use of artificial sweeteners among billions
of people in both industrialised and developing countries, the European Ramazzini Foundation considers its work on sweeteners to be of the highest priority for the protection of public
"We have planned and are conducting additional research, not only on aspartame, but also on other widely diffused artificial sweeteners and blends used in thousands of foods, beverages and pharmaceutical products."