BT, Britain's biggest broadband supplier, has been accused of limiting streaming video speeds at peak times, which is having a negative effect on iPlayer viewing for its customers.

A customer on BT's Option 1 deal with an 8Mbps line could have their speed cut to just 1Mbps between 5pm and midnight. A BT spokesman said the firm managed bandwidth "in order to optimise the experience for all customers".

"Traffic shaping" policies, as they're known, are implemented by almost all ISPs, so that one user downloading thousands of movies doesn't hurt the experience of others. However, most companies hide that information deep within the terms and conditions.

BT has said its traffic shaping is explained on its website, on the page describing its Total Broadband Fair Usage policy. That says: "We do limit the speed of all video streaming to 896Kbps on our Option 1 product, during peak times only".

The BBC has protested that this is giving consumers a less satisfactory viewing experience, streaming at 500Kbps, rather than the 800Kbps, 1.5Mbps or high-definition 3.2Mbps options.

Have you been affected by this or other traffic shaping issues? Drop a comment in the box below with your story.