Vodafone received no relief from tough market conditions in the first quarter, with a slowdown in Spain and South Africa resulting in another heavy drop in its key revenue measure.
The world's second-biggest mobile operator said the pace of decline in organic service revenue, which strips out items such as handset sales and currency movements, accelerated to 4.2% in the three months to 30 June.
That compared with a rate of 4%, including a full contribution from Italy, in the last quarter of its past financial year.
Chief Executive Vittorio Colao said the year had started in line with the company's expectations, and its performance had improved in markets such as Germany.
"Through our commercial actions and investment, our performance is beginning to stabilise quarter-on-quarter in several of our European markets, with customer appetite for 4G services clearly growing," he said.
The limited number of analysts who provide forecasts for the first quarter expected group service revenue to decline by 4.2%.
Vodafone Ireland sees fall in revenue and mobile users
Vodafone Ireland saw a fall in mobile customers during the quarter, while the amount it earns from each user was also down.
The company's Irish subsidiary, which is the country's largest player ahead of the newly-combined Three-O2, had almost 2.09m mobile customers by the end of June.
This was down 1.6% on the same figure at the end of April, when the network had over 2.1m mobile users.
Including customers using its other services, including fixed line connections, Vodafone Ireland had around 2.4m customers by the end of June.
However the amount it earned from each of these fell year-on-year during the quarter, down 2% to €28.60.
Vodafone Ireland said more than 60% of these were now smartphone users, while almost 70% of customers were using mobile internet and data services on their devices.
This has led to a significant jump in the demand for data, it said, with usage up 45% year-on-year.