MPs have demanded Amazon investigate reports that drivers delivering its parcels are regularly working shifts of more than 12 hours without a break, forcing some to urinate in bottles.

The chairs of the Commons Business and Work and Pensions Committees, Rachel Reeves and Frank Field, have asked the web giant’s UK chief Douglas Gurr to respond to a newspaper investigation into working conditions for those delivering orders.

The Sunday Mirror reported earlier this month that drivers were delivering as many as 200 Amazon boxes a day with little or no break.

The situation becomes so bad that drivers admitted they go to the toilet in plastic bottles as shifts regularly last longer than 12 hours.

Some said they often ignore speed limits in a desperate bid to meet targets set by the retail giant and its partners.

While others revealed they take home less than £160 a week, below the legal minimum for full-time workers.

In the letter, Reeves and Field write: “Regardless of the formal status of couriers delivering on behalf of Amazon, we would welcome your confirmation that you are investigating these issues and ask that you inform us what actions you are taking to ensure that those couriers contracted to deliver on behalf of your company are working safely and receiving fair pay.”

And Reeves told HuffPost UK that the Christmas rush for presents risks making things worse still.

“Amazon drivers should not be working for 12 or 14 hours a day,” the Labour MP for Leeds West said.

“It’s dangerous for them and it’s dangerous for us.

“And I’m worried that in the run up to Christmas the pressure on drivers will increase.”

Amazon UK did not respond to HuffPost’s requests for comment.