My engine warning light comes on when I am accelerating?

Hi, I drive a V reg Corsa club. When I am driving on normal roads, all is fine. However when I am driving on the motorway and accelerating, my warning light comes on and remains on until I press the brake or slow down. It has happened when I reach 70 mph, however today it was also showing when I was accelerating at 50 mph. Jut before the light comes on my car jerks as f the engine is struggling, I don't think it is losing power as I am still able to accelerate. Does anyone know what it could be? I have been to a garage, however they said they can only check it when the engine light is on all of the time. They said it can be anything from a faulty fuse to a serious problem. Does anyone know what it could be? I am sightly worried as I regularly use the motorway and want it fixed before I break down!!