The main groups supporting and opposing the Minnesotan constitutional marriage amendment have raised in total, around $16 million (£9 million), with equal marriage supporters having raised almost twice than those opposed to it.

The Associated Press reported that the total amount raised makes this the most expensive constitutional amendment campaign in the state of Minnesota’s history.

Both groups have spent most of the money they have raised so far, mainly on TV advertising, in an attempt to swap the voters’ opinions on the issue.

The main pro-equal marriage group, Minnesotans United for All Families, reportedly raised $3 million (£1.9 million) between mid-September and mid-October, and had received just over $500,000 (£310,000) since.

The total for the pro-equality group, including the latest figures, is more than $11 million (£6.8 million) since 2011.

Minnesota for Marriage, the anti-equal marriage group, raised $2.4 million (£1.5million) between September and October, and just under $700,000 (£435,000) since, bringing their totals to around $5.1 million (£3.2 million).

Minnesotans United reportedly still had $309,000 (£192,000) still in the bank on 22 October, but Minnesota for Marriage did not give a figure.

Most of the money donated to the pro-equality group was from some 62,000 individual donors, however recently some larger amounts had been given, including $125,000 (£78,000), which was pledged, by New York Mayor, Michael Bloomberg.

A large porton of the money given to Minnesota for Marriage came from the six Catholic diocese of Minnesota, which donated over $1 million (£622,000), including $100,000 (£62,000) just this week. The Minnesota Family Council, a socially conservative group which pursues biblical principles in public policy, also donated almost $1 million (£622,000).

Minnesotans United made the point that irrespective of the outcome at the polls, equal marriage will not be legal, but that the state’s constitution should not be used to discriminate against any group of people.

Minnesota state law already defines marriage as between one man and one woman, but on 6 November, voters will choose whether or not to make a constitutional amendment defining it as such.