The claim followed reports that bishops across the country will set aside one Sunday next month to drum up a fighting fund from parishes.
The Support Marriage Sunday plan is part of a drive to pay for an advertising campaign to oppose any push by the Scottish Government to legislate for gay marriage, according to a report in a Sunday newspaper.
Cardinal Keith O’Brien said: “Marriage is under threat and politicians need to know the Catholic Church will bear any burden and meet any cost in its defence.
“The bishops of Scotland are so concerned by threats to marriage that 26 August has been set aside as Support Marriage Sunday.
“We will use this opportunity to remind Catholics of the importance of marriage as a union of a man and a woman and to urge them to be generous in contributing to a special collection which will be used to support initiatives in defence of marriage.”
Same-sex marriage campaign group the Equality Network called the remarks “aggressive”.
Policy co-ordinator Tom French said: “For the Catholic Church to spend another £100,000 fighting LGBT equality in its self-declared war on gay marriage seems to be an aggressive, undemocratic and un-Christian thing to do.
“At a time of financial crisis, when poverty and depravation are on the rise, surely there are better things that this money could be spent on.”
He said most Scots supported same-sex marriage.
The Scottish Government is expected to publish the results of a recent public consultation on the issue this month.
Same-sex marriage supporters were expected to take their campaign to the Scottish Parliament today.