Tony Blair and Kofi Annan led demands today for an international force to be sent into southern Lebanon to stop Hezbollah attacks on Israel and Israeli retaliation.

One day after the G8 summit united to blame extremists for the violence and to urge restraint on Israel, Mr Blair and the UN Secretary-General went beyond the group’s agreed statement to declare that a stabilisation force was "essential."

They appeared to have gone further than either Israel or Washington wanted, with Israel saying it was premature to talk of such a force. Germany and Russia also have doubts, and Mr Blair last night admitted it was an "open question" whether it would be agreed.

Speaking after talks with Mr Annan, the Prime Minister said: "The only way we are going to have a cessation of violence is if we have an international force deployed into that area."

There are already 2,000 UN troops in southern Lebanon, but Mr Blair said the new force would have to be "a significantly larger contingent with a far more specific mission."

The UN Security Council will consider the idea on Thursday. Mr Annan said: "The Council should discuss it and pursue the package that the Prime Minister and I have discussed, including a stabilisation force and the sooner that discussion and the decisions are taken by the Council, the better it is."

But the Israeli Government is unlikely to find the idea acceptable unless the new force had a very different mandate to that of the 2,000-strong UN force - Unifil - already deployed in southern Lebanon.

Mark Regev, an Israeli prime ministerial spokesman, complained that neither the Lebanese Government nor the international community had ever acted to implement UN Security Council resolutions 1559 and 1580 calling for Hezbollah to be disarmed along with all other Lebanese militias.

"The fundamental problem is that difference between stated UN policy and the activities of UN personnel on the ground," he said. "UN policy says Hezbollah should be disarmed. UN people on the ground have a co-operative relationship with Hezbollah... Israel would not see a satisfactory situation as one in which the current situation was just amplified."

British officials said the force would be intended to stop the bombardment of Israel and implement the UN resolutions.

Mr Blair made plain that the force could only operate in circumstances where there had been a ceasefire. He played down the possibility of British troops being involved, saying the British military was already stretched. "It is not a role historically we have played in that region. We will work with other partners to see what can be done. It would be a multinational force."

Unifil, whose headquarters is Naqoura in southern Lebanon, was created in 1978. It currently has 1,991 troops assisted by 50 military observers and around 400 international and local civilian staff.

Its troops are currently drawn from China, France, Ghana, India, Ireland, Italy and Poland. It has an annual budget of $100 million.

The force was introduced after Israel’s March 1978 invasion of southern Lebanon. Its purpose was to restore peace and security and help restore the Lebanese government’s authority in the area. When Israel invaded again in June 1982 Unifil remained behind Israeli lines, providing protection and humanitarian relief to the local population.

When Israel withdrew in 2000 Unifil remained on the border and still has watch towers there. But it has frequently been the subject of angry exchanges between Israel and the UN over its effectiveness, as Hezbollah established de facto control over southern Lebanon.

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