Vendors offering mobile services such as ringtones and SMS news alerts could have such services temporarily suspended if they fail to allow users to easily stop subscriptions, regulator PhonepayPlus said on Thursday.

The watchdog for premium phone-paid services said it would clamp down immediately on vendors who did not offer easy get-outs as it launches an eight-week consultation on measures to improve business practices and boost customer trust.

"Any failure will mean we will use our emergency powers," PhonepayPlus Chairman Alistair Graham told a news conference. "We've got an immediate problem in the mobile sector and we want to get to grips with it."

Faster, third-generation telecoms networks and new devices such as Apple's iPhone are making premium-rate mobile services more available and attractive while increasing the need to improve business practices, PhonepayPlus said.

Sales of mobile premium-rate services rose 20 percent to 464 million pounds.

Yet the watchdog said a lack of trust meant most consumers never used such services and noted overall sales including landline and mobile services fell 10 percent to 1.07 billion pounds in the year to end-March.

Britain was hit by a series of scandals last year surrounding TV shows and quizzes that encouraged viewers to call in using premium-rate numbers but then misled them about the results, for example by keeping the competition open after they had chosen the winner.

Customer complaints in the past year more than doubled to over 8,000.

PhonepayPlus said consumers were too often signed up for subscriptions without realising it - and found it hard to unsubscribe.

They also received unwanted and sometimes expensive marketing messages, while pricing was unclear.

The watchdog said its concerns were shared by other European regulators, and said it had participated in a European Union-wide investigation into mobile premium services, whose results are due to be released later on Thursday.

"It's essential that we address this. Only by working together to build trust among consumers will we see a growing, sustainable, vibrant market for phone-paid services," said PhonepayPlus Chief Executive George Kidd.

The watchdog pledged to come up with measures to make costs and conditions clearer and to provide for easy ways of opting out of receiving promotional messages after consulting with operators and so-called aggregators.

Aggregators such as MX Telecom, mBlox and WIN link telecoms carriers and content providers such as music labels and video producers.