SINGAPORE - One in six mobile phone users in Singapore is now opting for line-only plans, according to an official consumer awareness and satisfaction survey.

This is the first time the popularity of these plans - which do not come with a subsidised mobile phone, and are thus cheaper - is made public.

Telcos have so far not revealed how many of their post-paid subscribers are on line-only plans due to the commercial sensitivities of the information.

The latest survey by the Infocomm Media Development Authority (IMDA) was conducted between March and May this year involving about 1,500 households.

It was last conducted in 2014.

The latest survey also shows an overall increase in consumers' satisfaction with the quality, price competitiveness and customer care services of telcos in Singapore over the past four years.

But consumers also highlighted the need to reduce hotline waiting times and proper follow-up to solve complaints, among other issues, according to IMDA in a statement on Tuesday (Dec 11).

Ms Aileen Chia, IMDA's deputy chief executive and director-general (Telecoms & Post), said these are "encouraging signs pointing to a positive attitude towards a digital future and a willingness of our service providers to meet consumers' rising service quality expectation".

Telco M1 was the first to roll out bargain line-only mobile plans in July 2015.

It offered a 5GB mobile data bundle, 300 minutes of talk-time and 1,000 SMS and MMS for $30 a month.

The package was less than half the prevailing price for a similar plan at that time.

Rivals Singtel and StarHub followed suit later that year, offering more discounts for line-only plans.

The telcos' moves came at a time when China phone makers such as Xiaomi, Huawei and OnePlus were rolling out low-cost smartphones so consumers need not sign expensive two-year mobile service contracts in exchange for massive subsidies for their smartphones.

After new virtual mobile telco Circles.Life launched in Singapore in 2016, competition intensified even more as all the telcos slugged it out to retain customers.

For instance, one key improvement was the return of unlimited mobile data features and plans to cater to data-heavy users.

The move reversed a trend of lowering data bundles that started in 2012 when 4G services were launched.

This could have contributed to the biggest increase in consumer satisfaction towards mobile data services as captured by the latest IMDA survey.

Respondents were asked to rate their satisfaction levels on a scale of one to five for fixed line telephone, mobile telephone, fixed broadband, mobile data and international roaming services.

Mobile data service saw the biggest increase in mean satisfaction scores given by survey respondents for quality of service.

Respondents were also more satisfied with the price competitiveness of all telecommunication services - except fixed line telephone - this year compared with 2014.

The mean score for the price competitiveness of international roaming services increased the most, according to IMDA.