Publicans have been warned that leaving their doors unlocked before opening time makes them a prime target for thieves.
The warning follows a case in Leeds earlier this month where a gang walked into an unlocked pub, tied up the cleaners and lay in wait for the assistant manager who was then forced at gunpoint to hand over the contents of the safe.
Pubs are particularly vulnerable to such attacks, according to trade leaders and police, because many licensees leave doors unlocked after cleaning staff start work.
Tony Payne, chief executive of the Federation of Licensed Victuallers Associations (FLVA), said: "I am able to walk into a lot of pubs before opening time and if I can do that then any person off the street could.
"You don't see any other shops or stores leaving their doors open and neither should pubs. Licensees have to become a bit more security conscious."
Police in Leeds said the attack, on the Queens Court pub in the city centre, could have been prevented if the doors had been locked until opening time.
A spokeswoman for West Yorkshire Police said it was important all publicans were aware of the risks of leaving doors unlocked before the pub officially opened.
She said: "We urge all licensees to take precautions to make sure their premises are secure.
"It is also important that licensees are aware they can contact local police for advice about general security and more specific problems," she added.
The FLVA is planning to re-issue its security advice booklet to members following the Leeds attack and Mr Payne said he would advise all licensees to re-assess the security of their premises.