Rome (AFP) - Italy on Wednesday joined the rest of the Western world in extending legal recognition to same-sex relationships with parliament overwhelmingly backing gay civil unions after a long battle to overcome opposition led by the Catholic church.

Lawmakers in the lower-house Chamber of Deputies voted 372-51 in favour of the legislation with 99 abstentions after an earlier vote of confidence in the government on the issue had been equally comfortably carried, making approval of the bill itself automatic.

The long-awaited and much-disputed legislation was hailed as a landmark but also criticised as falling short of full equality for gay couples, particularly in relation to adoption and marriage rights.

Gay rights activist Federica Frasconi, 26, was in a small crowd outside parliament for the votes.

"We hope the next law, which we will all fight for ... will be for marriage and adoption. And I hope there will be also a law against homophobia," she told AFP.

Monica Cirinna, the senator who was the main author of the bill, said she expected the first civil union ceremonies "no later than September" and dismissed opponents who vowed to seek a referendum aimed at overturning the law.

- 'Reject medieval bigotry' -

"We will welcome that with open arms. It will allow us to push on to equal marriage even sooner," she said. "Italy will reject medieval bigotry and conservativism."

Marilena Grassadonia, president of the Rainbow Families campaign group, said it was a "historic day" for Italy but that celebrations would be muted because of the failure to secure adoption rights.

"What mother or father would attend a party their children are not invited to?" she said.

Prime Minister Matteo Renzi, who had backed the bill but largely stayed out of the debate, called the confidence vote to short-circuit potential last-minute blocking or delaying amendments by opponents of the legislation, who include rebels in his own party as well as the Catholic right.

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"Today is a day of celebration for so many people," the centre-left leader wrote on his Facebook page, framing the vote as another victory for his reform programme.

"We are writing another important page of the Italy we want," he said.

The government used the same confidence vote tactic to get the bill approved by the upper house Senate in February, but only after the original text had been diluted to appease opponents threatening to scupper it altogether.

A draft article that would have granted gay couples the right to adopt their partners' biological children was dropped.

While adoption will not be ruled out entirely, family judges will decide on a case-by-case basis.

- European Court pressure -

In the face of concern that civil unions would be too similar to marriage, references to a need for faithfulness were also removed.

Gay couples will be able to take each other's names and inherit each other's residual pension rights, but critics say the new rules fall short of legal protection offered to same-sex couples in other European countries, Canada and the United States.

Several previous attempts to legalise civil unions in Italy have foundered in the face of opposition orchestrated by the Catholic church.

The current bill risked running aground over the adoption clause, with critics insisting it would open the door to surrogacy, which is illegal under Italian law.

Renzi's Interior Minister Angelino Alfano was among the most fervent opponents of providing a legal framework for surrogacy, saying in January the the use of paid surrogate mothers should be treated like a sex crime.

Italy had been under pressure to get a bill onto the statute book from the European Court of Human Rights.

Judges at the court ruled last year that Italy had breached its commitments under the European Convention on Human Rights by denying gay couples legal unions.

Polls suggest Italian public opinion has moved decisively in favour of civil unions in recent years but that a majority of voters remains opposed to extending equal adoption rights to gay couples.