Israeli Opposition leader Tzipi Livni has visited Britain – but although her trip was billed as showcasing the change to the law on universal jurisdiction, it was in fact protected by an altogether different legal status.

Ms Livni met Foreign Secretary William Hague, at his invitation, at the Foreign Office in London last Thursday.

She was the first senior Israeli to visit Britain since the government changed the law last month. But in doing so, the Kadima leader raised questions over how the law would be implemented.

Mr Hague said he was "delighted" to welcome Ms Livni. He added: "It was an appalling situation when political abuse of our legal procedures prevented people like Ms Livni from travelling legitimately to the UK."

Last Tuesday, 48 hours before Ms Livni's visit, Director of Public Prosecutions Keir Starmer QC was presented with an application to authorise her arrest by the Palestinian Centre for Human Rights.

The PCHR was working with lawyer Daniel Machover on behalf of a Palestinian whose police officer brother was killed on the first day of Operation Cast Lead in December 2008. It said the government had "abused the law in order to ensure that Ms Livni escapes accountability".

Mr Starmer began following the new procedure, set out in the Police Reform and Social Responsibility Act, to consider if there were sufficient evidence for an arrest warrant to be issued. He sought advice from Attorney-General Dominic Grieve MP.

But when the pair asked the Foreign Office for clarification of the reasons for Ms Livni's visit, they were informed that Mr Hague had given it "special mission" status.

This status is similar to diplomatic immunity and affords visitors protection from legal action for the duration of their trip. No court can question the designation of a mission as "special". Consideration of evidence under the amended universal jurisdiction law therefore became irrelevant as Ms Livni was protected by the "special mission" status.

The Crown Prosecution Service issued a statement on Thursday as Ms Livni met Jewish leaders and students.

It said: "The DPP refused to give his consent to the private prosecutor to make an application to the court for an arrest warrant. In considering this application, he consulted the Attorney-General, but the decision [was] his."

Rumours at the weekend suggested that the Ministry of Justice, which oversaw last month's law change, was unhappy with the use of the "special mission" status for Ms Livni.

But these were dismissed on Monday. The MoJ said it was content that the law would have been applied in the correct way if the special mission status had not been granted to Ms Livni's visit.

While the Foreign Office's use of the special mission status protected Ms Livni, its application is limited. It requires a lengthy legal process to prove that the visitor it is being applied to is representing their country, and that the UK government has agreed to their trip.

The amended universal jurisdiction law thus remains untested. It was General Doron Almog's planned visit five years ago which sparked the controversy and ended with him unable to leave a plane at Heathrow before immediately returning to Israel.

He said a fortnight ago that he would come to Britain next year to speak to supporters of the Aleh charity, which works with disabled children.

It said this week that he still intends to visit in January but will assess the potential for his arrest before going ahead with the trip.