UPDATE 2-UK warns of wide disruption if businesses do not prepare for end of EU transition

(Adds context, details of report)

By Kate Holton and Guy Faulconbridge

LONDON, Sept 23 (Reuters) - Britain faces jammed borders and 100-km lorry queues at the end of its transition agreement with the European Union in January unless businesses take the deadline seriously and prepare for it, the government said on Wednesday.

Britain formally left the bloc in January but remains in a status quo transition period that expires at the end of this year. The government assumes EU member states will impose third-country controls on Britain at the end of the transition period.

Cabinet Office Minister Michael Gove warned there would be change at the end of the transition period whether stalled talks with the EU produce a deal or not, but shifted the responsibility for minimising disruption onto businesses.

"The consequences of a lack of business preparedness will be not just economic opportunities missed for those companies who don't prepare, but potentially much wider disruption," Gove told parliament.

Earlier, the government warned British trucks could face delays of up to two days to enter Europe and queues of around 7,000 lorries after Britain leaves the bloc, disrupting imports and exports of crucial goods.

This disruption would peak in January, but the speed at which it would ease depended on how quickly businesses adapted to new processes, a worst case scenario analysis published by the government said.

Gove, the minister overseeing the Brexit talks, told the logistics and freight industry that truck drivers would face new customs controls and processes irrespective of whether a trade deal can be agreed between the two sides.

He said under the government's reasonable worst-case scenario, up to 70% of trucks travelling to the EU might not be ready for new border controls.

"This could lead to maximum queues of around 7,000 port-bound trucks in Kent (in southeastern England) and associated maximum delays of up to two days," he said.

A government spokesman said this was not a forecast or prediction of what will happen but rather a "stretching scenario". (Editing by Michael Holden and Stephen Addison)