Americans see email and the Internet as the most important tools for productivity at work, and still prefer landlines over cellphones for the office, a study showed Tuesday.

The Pew Research Center found 61 percent of those surveyed cited email as "very important" for their jobs and 54 percent said the same for the Internet.

The figures were even higher for office-based workers.

More than one in three surveyed said the landline phone was an important tool for work, compared with 24 percent for a mobile or smartphone.

And despite the rise of social networks like Facebook and Twitter, just four percent in the survey said these platforms were important for the workplace.

"Email is to the digital age what stone-sharpening tools were in the prehistoric age," said Lee Rainie, director of Internet, science, and technology research at the Pew Center.

"Email has proven its worth on the job as the foundational 'social media' day by day even as rival technologies arise.

"It was the killer app 45 years ago for the early Arpanet and it continues to rule workplaces despite threats like spam and phishing and competitors like social networking and texting."

Contrary to concerns that technology is a distraction, the survey found 46 percent said digital tools made them more productive, compared with seven percent who said their productivity fell.

Half of the respondents said technologies allowed them to expand the number of people with whom they communicate, and 39 percent said they had more flexibility at work due to digital tools.

But one in three said the new landscape increased the time they spent working.

The importance of email in the workplace has been documented for some time. In 2002, Pew Research Internet surveys showed that 61 percent of American workers were using email at work and in 2008, reported that 62 percent of working US adults were "networked," meaning they used the Internet or email in the workplace.

- Office and away -

For office-based workers, these tools are markedly more important, Pew found: 78 percent of office workers cited email as an important tool compared with 25 percent who don't work in an office.

And the Internet was seen as vital for 68 percent of those in an office, and 26 percent of non-office employees.

For those who work away from their main workplace, the Internet and cell phones are key tools, Pew found.

Among the nearly 60 percent of employed Internet users who go outside of the workplace at least occasionally, half say the Internet and cell phones are "very important" to allowing them to do their job.

The survey also found that nearly half -- 46 percent -- of employees said their workplace blocks access to certain websites or imposes rules about what they can say or post online.

One in four said their company encourages employees to use the Internet and email to promote the organization, but more than half said this was not the case.

"These respondents highlight how workplaces in the Knowledge Economy are differently organized and have different connections to customers and competitors from workplaces designed to suit the Industrial Age," said Rainie.

The report is based on an online survey conducted September 12-18 of 1,066 adult Internet users, which included 535 employed full-time or part-time. The margin of error was estimated at 4.9 percent.