Pendle Water has been cutting away land by the motorway in Brierfield and is now just 40m from the bottom of the embankment.

One resident says the river has gouged out 20 yards in the past 12 months - and two yards in a few wet days over the weekend!

Lancashire County Council and the Environment Agency say they will keep tabs on the situation, and do work to protect the road when needed.

The section under threat is close to Junction 12 and Quaker Bridge at Brierfield.

The resident said: "The river is moving very rapidly towards the embankment. I have watched its progress over the last few years, ever since the river's path was changed to allow building the Lomeshaye Industrial Estate.

"I estimate the embankment will start to be eroded within 12 months, closing the motorway in the process and presenting us all with a very serious transport problem - businesses, schools, colleges, the entire region suffering travel chaos. The cost could run into millions, if not tens of millions.

"Unless serious remedial action is taken, and taken quickly, we will lose the use of the M65 in less than a year."

A spokesman for Lancashire County Council said: "We are aware the river has been changing course and moving towards the motorway. Although there is no cause for immediate worry, we are going to bring the matter to the attention of the Environment Agency. The river has been in flood over the last few days and this does not pose a particular problem."

An Environment Agency spokesman said an officer would be revisiting the site within the next few days, and any issues would be reported to the appropriate authority.