Lauren Booth is the sister-in-law of Middle East envoy Tony Blair
Lauren Booth, human rights activist and sister-in-law of the former British Prime Minister Tony Blair, has said she is being prevented from leaving Gaza.
Ms Booth arrived in the Gaza Strip on a "peace boat" to publicise Israel's blockade of the Palestinian territory.
But she said the Egyptian and Israeli authorities had prevented her from leaving Gaza three times.
Mr Blair, now an international envoy to the Middle East, is currently in the region meeting senior Israeli leaders.
'Non-violent resistance project'
Israel tightened an economic blockade on Gaza after Hamas forces violently seized control from Fatah in June 2007.
The borders between Gaza and Egypt and Israel are closed to people most of the time.
About 45 people - including Americans, Palestinians and Israelis - took part in the "peace boat" mission last week.
Two vessels - named Liberty and Free Gaza - arrived in Gaza on Saturday 23 August carrying 200 hearing aids for children and 5,000 balloons.
The president of the Free Gaza Movement, Greta Berlin, said it was "a non-violent resistance project to challenge Israel's siege of Gaza".
When the boats returned to Cyprus, Ms Booth and a few other activists remained in Gaza.
Now the sister of Mr Blair's wife Cherie has said she wants to go home but has been prevented - along with three other foreign nationals - from leaving Gaza three times, once by the Israeli authorities through the Erez crossing and twice by the Egyptians via Rafah.
Ms Booth told the BBC: "I'd actually like to say 'Thank you very much' to the Israeli authorities at Erez for giving me this fantastic chance to feel just exactly what it is like to be inside what is effectively the world's largest internment camp, where individuals who should have the right to travel under international law are withheld in a 40km by 10km camp."
She said she was missing her two children who kept asking her, "Mummy, why can't you come home? Have you done anything wrong?"
"No, under international law I've done nothing wrong, but for some reason I am effectively being imprisoned here by authorities who wish to punish human rights activists who have come to view the situation in Gaza," she said.
In the past, Ms Booth has publicly criticised some of Mr Blair's government's foreign policy decisions.
Mr Blair now acts as the International Quartet's special envoy to the region. There is no word yet from his office about any official efforts to get Ms Booth out of Gaza.
She said she did not want to appeal to him "on such a small matter as my own liberty" and instead wanted him to focus on the Palestinians themselves and the "terrible poverty entirely created by the siege" in Gaza.
In July, Mr Blair cancelled a planned visit to Gaza after being informed by Israeli authorities of a specific security threat.
But Ms Booth said she had been treated "marvellously" by the authorities in Gaza, and added about her brother-in-law: "It is his duty as Middle East envoy to make sure he makes the effort to come here."
The British Consulate in Jerusalem said it was in close contact with British nationals in Gaza.