The number of unemployed in France rose 16,200 to 3.55 million in May.
With those in part-time employment or on short-term contracts added, the figure leapt 69,600 to 5.41 million.
But an exceptional measure taken by the Pôle emploi employment service have rendered the figures "uninterpretable", according to Labour Minister François Rebsamen.
Job centres sent out reminders by SMS and voicemail to job-seekers to bring their situation up to date, almost doubling the rise, the minister said.
"At the end of the year we'll see, I hope, a phase of stabilisation and then a drop in the number of jobseekers," he said on Wednesday.
He pointed to forecasts by the OECD and France's unemployment insurance body predicting a slight drop in the jobless figures in the second half of this year.
Like the Bank of France and the state statistics office Insee, they expect growth of over one per cent, which would affect employment.
Earlier this month Insee, which calculates its unemployment figures differently to the employment service, said there had been a fractional drop in unemployment in the first quarter of 2015.
Unemployment has risen 630,000 since President François Hollande was elected in 2012 and two million since the financial crisis of 2008.
In August 2013 a bug that led to a failure to send out some reminders caused to an apparent drop in France's unemployment figures, which was reversed in the statistics of the following month.