African countries against the virus. WHO fears that the boycott will turn northern Nigeria into a breeding ground for polio, endangering public health across west and central Africa. In recent months, an outbreak of polio in Kano, one of the Nigerian states which suspended immunisation, has spread the disease to seven neighbouring African countries where it had previously been eradicated. Unicef's spokesman, Gerrit Beger, said: "Nigeria is the weakest link in the global campaign to stop the transmission of the polio virus. "We are using the same vaccine in Nigeria that we use everywhere else in the world. "It is saddening because this is a lost opportunity for children to be immunised. Any delay in immunisation is a threat to the health of children in Nigeria. He said that the number of children contracting the virus has been reduced from 350,000 worldwide in 1988 to less than 1,000 last year. But he warned: "By further delaying immunisation we risk reversing our gains." Last August, the governor of Kano state suspended the polio campaign and set up a committee to investigate the infertility claims. In January the committee said they had found traces of the female hormone oestrogen that could affect fertility. Tests elsewhere have not found hormone contamination and experts insist the vaccine is safe. Nigeria's Niger state allowed the vaccinations to start on Monday, but ordered them stopped at the end of the day. A spokesman, Mahmud Abdullahi said: "Polio immunisation has become controversial. So to be on the safe side, the Niger state government has decided to suspend polio immunisation until we're reassured it's safe." In Kaduna state, where the vaccine was banned last year, officials relented on Monday and allowed the programme to go ahead. Health workers chalked ticks on the houses of accepting families, and the letter R on the walls of those who refused. Nigeria's federal government sent politicians, scientists and religious leaders abroad this month to observe how the vaccine is produced and tested. The results of this investigation are due to be published later this week. Muslims in Nigeria have been wary of medical programmes after 1996 when families in Kano state accused the drug firm Pfizer of using an experimental meningitis treatment on patients without fully informing them of the risks.

Home Secretary Gets Tough Over Terror

Mr Blunkett challenges critics to help him square the circle The home secretary is preparing to unveil new anti-terror measures, thought to include the use of secretly-taped phone calls as evidence. Other changes are predicted to include the hearing of parts of some trials in secret, without a jury. David Blunkett told BBC's Newsnight he had been told it was inevitable the UK would face a terrorist attack. On Wednesday he will detail the expansion of MI5, with 1,000 new staff, many of them Arabic and Urdu speakers. Mr. Blunkett told the BBC the security services needed more powers to apprehend terrorists before they strike. But MPs will debate criticisms of current laws allowing foreign terror suspects to be detained without trial. 'Secret trials' Some of the anti-terror powers introduced after the 11 September attacks only last until 2006. Mr. Blunkett says the paper will show what other countries are doing and recommendations from reviews of current British laws. He suggested the law could be changed to allow secretly-taped phone conversations to be used in court. Hearing some cases partly in secret before specially-vetted judges with no juries so intelligence sources are not compromised, is among the ideas likely to be included. POSSIBLE IDEAS Pre-emptive action against terror suspects Civil action against those on the fringes of terror groups Specially-vetted judges for sensitive evidence Part-secret trials for Britons     Defendants could also be barred from hearing certain evidence mirroring what happens for foreign terror suspects. The Home Office insists no decisions have been taken on the proposals, which have sparked criticisms from lawyers and human rights groups. Mr. Blunkett said the head of MI6 had told him a terror attack on Britain was a case of not "if" but when. "Whatever we do - and we are doing everything we can - we cannot guarantee, and nor should we pretend to, that we can protect ourselves forever by security measures alone," he told BBC Two's Newsnight.