Pendle council licensing officers and police could extend existing bans or impose a drinking banning order (DBO) which can last up to two years.
It is the second year that the letters have been sent to offenders, as members of the three local Pubwatch schemes prepare for a trouble-free Christmas.
Mick Armfield, Pendle Council’s licensing enforcement officer, said: “There are currently 50 offenders on the Pubwatch schemes.
“It’s a tough message but it’s important they understand that trying to break the ban is totally unacceptable and will not be tolerated.”
All licensees have pictures of the offenders and will inform the police if anyone tries to enter their venue.
They will also record their details so that the police can apply to Magistrates Courts for a DBO where necessary.
Noel Buckley, licensee of the Crown Hotel in Colne and joint Chair of Colne Pubwatch, said: “It’s really important that all those on the banned lists take heed of the warning letters.
“Failure to do so can lead to their ban being extended or much worse, a DBO being imposed.
“Over the coming weeks many people will enjoy a festive drink in Pendle’s pubs and clubs and we welcome initiatives like this which help to ensure a safe and enjoyable night out.”
PC Mark Driver, Divisional Police Licensing Constable, added: “We’re committed to working in partnership with our local Pubwatch schemes to make sure that those banned don’t cause further problems.
“The warning letter was successfully introduced last year.
“The fact that there was only one incident throughout the whole festive period meant it was a success.
“We hope that it will have the same impact again this year.”
Councillor Eileen Ansar, chair of the licensing committee, said: “It’s fantastic that something so simple works so well.
“It’s really important that we make sure our pubs and clubs are an enjoyable place to be, particularly over Christmas and New Year.
“This is a time when friends and families come together and don’t want to be intimidated by trouble-makers.”