Tim Kaine, the Democratic Vice-Presidential candidate, is under fire for reportedly changing his position to support the overturning of a key amendment in US law which prevents government funding for most abortions.

Hillary Clinton's running mate had until recent weeks supported the Hyde amendment, which since 1976 has prohibited certain taxpayer funds – generally those through the Department of Health and Human Services – from going towards abortions, except in cases of rape, incest, or when the life of the mother is deemed to be at stake.

Kaine, a Catholic, has previously said he was opposed to abortion privately if not politically and has supported the Hyde amendment.

But Clinton's platform for the Democrat party for the first time calls for the repeal of the amendment.

On July 6, Kaine was asked by The Weekly Standard about the plan. Kaine said that he was not aware of change, but added: "I have traditionally been a supporter of the Hyde amendment, but I'll check it out."

Then, on July 22, Kaine was officially announced as Clinton's Vice Presidential candidate. On July 26, CNN reported that the Virginia senator had changed his position on the Hyde Amendment.

Marjorie Dannenfelser, president of the pro-life Susan B. Anthony List, said: "Just 20 days ago Senator Kaine said he supported the Hyde Amendment, which stops taxpayers from funding abortion on-demand. What has changed? The Democratic Party has become so bound to the abortion industry that there is no room for conscience. Before he could be considered fit for the role of VP to Hillary Clinton, Kaine had to divest himself of even the appearance of moderation on the abortion issue."

She went on to call Kaine an "extremist": "Clinton, Kaine, and [Planned Parenthood head Cecile] Richards are absolute extremists pushing the Democratic Party further and further on abortion, alienating the one-third of Democrats who call themselves pro-life."

Kaine has previously said of abortion: "I have a faith-based opposition. I will work in good faith to reduce abortions."

As the Washington Post has observed, Kaine "promoted abstinence-only sex education (and later slashed funding to the programme, citing research that found it wasn't effective). He authorised the sale of 'Choose Life' license plates to fund religious counseling clinics that discouraged abortion. He backed Virginia's 'informed consent' law, which requires women seeking the procedure to undergo medically unnecessary ultrasounds. In short, he was conservative on reproductive issues, by his party's standards."

Now, however, the "extreme" Democrat agenda on abortion this election year, to which Kaine has signed up, has led Michael Wear, Obama's Catholic former director of faith outreach, to call the Clinton campaign's position "morally reprehensible".