Queuing on slip road

On Monday when exiting the London bound carriageway at junction 4 cars were queuing on right hand side of slip road back down onto the motorway, despite the fact that the slip road can accommodate two lanes of traffic. Need signage asking motorists to use both lanes and to filter at end of slip road onto roundabout. Have come across this problem on numerous occasions and is potentially dangerous and causes motorists who use left hand lane to be seen as queue jumping which can cause "road rage". Traffic there now is particularly high because of the ongoing road works at junction 5.