They work unsocial hours, performing the tasks no-one else would do - but that is still not enough to get them invited to the office Christmas party.
Most cleaners are left out of party planning, the survey found
A survey has found two out of three office cleaners are given the brush off by staff organising the work bash.
The poll of 200 workers from schools, printing firms and charities was led by the British Cleaning Council.
The council said it was "saddened" that cleaners were being overlooked in the season of goodwill.
In one case, the survey heard from a cleaner who had worked for a company for eight years before she finally received an invitation to a work function.
She was so angry it had taken so long to come that she turned down the offer.
BCC chairman Paul Pearce said: "Despite their best efforts to keep business premises clean and tidy for office staff, cleaners continue to remain an invisible presence in the working world.
"We are saddened at such findings as without our silent army of cleaners we'd be working in squalor.
"Many office employees don't even know their name. It would be great to see companies buy their cleaners a Christmas present at the very least."
The council said two million people are employed as cleaners in Britain, around one in 12 of the country's workforce.
But the survey found cleaners feel they are not considered part of the office staff, particularly if they are employed by cleaning contractors.
"I would be interested to see how attitudes would change if our cleaners took a holiday," Mr Pearce said.