LONDON, Dec 20 (Reuters) - Nearly a third of Uber's 50,000 drivers in Britain are logged into the app for more than 40 hours a week, whilst just under 8 percent are online for more than 60 hours, the company said in a letter to parliamentarians published on Wednesday.
The app has been attacked by trade unions and lawmakers who say that some of its drivers are working excessively, one of many criticisms it has faced about its business model.
A total of 2.6 percent of drivers are logged in for more than 70 hours a week and 0.8 percent for longer than 80 hours, according to the firm.
But Uber's Head of Public Policy in Britain and Ireland Andrew Byrne said being logged on was not the same as the number of driving hours.
"Individuals are able to turn the app on and off at any time as well as decide when to take requests - this means that an hour logged into the Uber app is not the same as an hour of work," he said in a letter responding to questions from parliament's business, energy and industrial strategy (BEIS) committee.
"Drivers often do not confirm trips that are sent to them," he wrote.
Uber has faced setbacks in Britain this year, losing a case on workers' rights, being stripped of its London licence and hunting to find a replacement for its boss.
Byrne said the app was planning to introduce a tool which will limit driving hours in January and would write again to lawmakers.
The committee chairwoman said she wanted Uber to provide details of the plans early next year.
"Uber's own stats indicate they have drivers who are logged in for more than 70 and 80 hours a week, a fact which would be a matter of concern for anyone potentially booking one of these Uber drivers," said Rachel Reeves.
"We expect Uber to update the BEIS Committee in the New Year with the specific details on how the driver hour limits will work in practice." (Reporting by Costas Pitas; editing by Stephen Addison)