With friends like those in the Wisconsin legislature, supporters of a constitutional amendment to give the District of Columbia full voting representation in Congress do not need any enemies.

In the first action in six months in the staggering ratification drive, the Wisconsin Assembly approved the amendment Tuesday by a vote of 68 to 30. The Wisconsin Senate had given the amendment its support last April, by a vote of 19 to 13.

But here's the catch: Before the ratification vote yesterday in Madison, the Assembly tacked on a statement blasting Congress for failing to give the District of Columbia full home rule powers along with congressional representation.

The additional wording is icing on the cake, at best, because no state can change a constitutional amendment. It must either ratify or reject it. So the grand-sounding extra words, "congress should serously consider retrocession and statehood as alternatives to this constitutional band-aid, which perpetuates the home rule sham by Congress," only forces the issue back to the state Senate for another vote. If the Senate concurs, Wisconsin would become the seventh state to ratify the amendment, the extra language notwithstanding.

Supporters of the amendment are suspicious of the Assembly's motives. They believe the action was encouraged by the amendment's opponents in the hope that the Senate, given a second chance, would reject it.

"I'm apprehensive as to why it was done," said Senate President Fred Risser (D-Madison), a strong supporter of ratification. He noted that the change was offered by Assembly Speaker Edward Jackamonis (D-Waukesha), who, he said, "has never particularly liked the amendment." An aide to Jackamonis denied that the action was an opposition tactic, although he said the speaker was ambivalent" about the amendment.

Here at home, Richard Clark, board chairman of the Self-Determination for D.C. coalition, said the action "sets the stage for the worst kind of hypocrisy."

However, Assembly Majority Leader Jim Wahner (D-Milwaukee) die not interpret the change in wording as "a ploy" by opponents. Wahner said he supported the change, "even though I was unenthusiastic about it."

Wisconsin supporters of the D.C. coalition had been following the action in Madison closely, and told Clark last night that the overwhelming vote in "no way" reflected the level of support in the legislature for D.C. voting rights. Supporters had hoped that Wisconsin would be the next state to ratify the proposal, but they knew it would be a close call.

Senate President Risser said he will bring up the amended version for consideration today. The Wisconsin ledislators will recess for the year on Friday. If the Senate fails to concur, consideration of the amendment can pick up where it left off in January.

The Assembly's action Tuesday was the first of any kind on the amendment since last April 26 when the New Hampshire legislature became the 10th state to reject it. If the amendment is to become law, 38 states must approve it, by August 1985.