But Livni's office said in a statement after the reports that she had declined a request to attend the event in London due to a scheduling conflict and not because of fears of being arrested.
'Threat of prosecution'
The British foreign office issued a statement on Monday saying it was looking into the incident and its possible effect on the peace process.
Al Jazeera's Lauren Patterson reports on the confusion over the Livni warrant
"The UK is determined to do all it can to promote peace in the Middle East and to be a strategic partner of Israel," it said.
"To do this, Israel's leaders need to be able to come to the UK for talks with the British government. We are looking urgently at the implications of this case."
Bill Bowring, a professor of law at the University of London, said the threat of prosecution is making international travel increasingly difficult for Israeli officials.
"This has happened before. It's under quite old legislation, under the fourth Geneva Convention of 1949," he told Al Jazeera.
"Basically what it says is that if a person anywhere in the world commits grave breaches against civilians then that person should be arrested and prosecuted wherever they turn up in the world."
Israeli land, air and naval forces began bombarding the Gaza Strip last December, saying that it wanted to stop rocket attacks by Palestinian fighters.
A UN-sponsored report, known as the Goldstone report, has called on both Israel and the Palestinians to investigate accusations of human-rights violations committed during the conflict.
The report accuses both Israel and Hamas of war crimes, and was endorsed by the UN General Assembly last month by a margin of 114 to 18, after two days of debate.
Forty-four member-nations abstained from voting.
The report, which was compiled by a panel led by Richard Goldstone, a South African judge, had already been endorsed by the UN Human Rights Council, which sponsored the fact-finding commission.
Most of the criticism in the Goldstone report was directed towards Israel's conduct during the offensive, in which it concluded that Israel used disproportionate force, deliberately targeting Gaza civilians, using them as human shields, and destroying civilian infrastructure.
More 1,400 Palestinians were killed in the offensive, while 13 Israelis, including 10 soldiers, died over the same time period.