They warned vegetation could be at its thickest at this stage of the year while maintenance may not be the priority for stretched councils.
GEM chief executive Neil Worth said: “Road signs provide vital information for drivers, who will plan their speeds and actions based either wholly or in part on what the signs tell them.
“If you can’t see a sign, then your ability to make safe decisions is compromised, especially if you’re on unfamiliar roads.
“Nourished by recent rain, vegetation at this time of year tends to be at its most prolific, meaning more and more signs risk being partially or completely covered. It’s a growing menace that puts road users at risk.”
“It is vital for road safety that trees, bushes and branches are not allowed to obscure important information, and that everyone using the roads has a clear view of speed limits and other signs.”
A survey from Transport Focus revealed that almost one third of drivers had missed a motorway exit due to concealed road signs.
The group launched their independent ‘Sort My Sign’ website earlier this year where drivers can report poor quality signs which will be used to lobby the government.
The site allows road users to enter a location, road name or postcode and enter details of any issues.
GEM Motoring Assist says road users can reduce the risk of being caught out by blocked road signs by taking some very simple precautions.
The company says knowing the shape of a sign is sometimes all a driver will need for vital decisions.
A spokesperson said: “For example, ‘Stop’ is the only octagonal-shaped sign, and it means exactly that. Your wheels must stop turning.
This method is the same for the ‘Give Way’ sign which is the only upside down triangle on the road network.
For those traveling near a country road, GEM says looking far ahead into the distance could also help those unable to read signs.
A house, church or any other bulldogs in the distance will likely mean the speed limit has changed to 30mph although this could be lower in some areas.
They warn drivers that they should never take risks in making last minute swerves if they read a sign too late.
Instead road users should carry on driving until the next junction and only make a change when it is safe and legal to do so.