Wales' Premiership rugby clubs say they are "in discussions" with the Welsh Rugby Union to change their fixture list for 2015-16.
Some clubs in Wales' semi-professional division have no scheduled home games in December, 2014.
Those not involved in the British & Irish Cup - which includes English and Irish sides - are affected and say it is "an issue".
The Welsh Rugby Union has been asked to comment.
There are 12 Premiership clubs: Newport, Bridgend, Cross Keys, Ebbw Vale, Cardiff, Pontypridd, Aberavon, Neath, Bedwas, Llandovery, Carmarthen Quins and Llanelli.
Their chairman Chris Clarke, who is also secretary of Cross Keys, said: "It is not just the lack of money through the gate, there is match sponsorship and bar trade to think about as well.
"Finance is what the game runs on at the moment so this is a sensitive issue with a number of clubs."
Of the eight sides not involved in the British & Irish Cup (BIC), Cardiff have the most home Premiership fixtures in December, with three at the Arms Park.
Ebbw Vale, Llanelli, Llandovery and Neath each have one while Bridgend and Newport have none.
Newport secretary Dennis Bennett said: "Everyone can see that the way the fixture list is set up is not helping us at all.
"Supporters get out of the habit of going to matches.
"It is not doing the players any good and we really need to do something about it."
Bennett said it was difficult to put a figure on how much money his club were missing out on, but admitted there was an "obvious" loss of revenue.
He also revealed that at the start of this season the Premiership clubs had discussed setting up an alternative competition for sides not involved in the BIC.
The clubs say they are hopeful of a resolution for next season.