Nations united over Libya as Cameron says pressure on Tripoli beginning to tell – but G8 rift remains over Syria

Colonel Gaddafi has beenleft diplomatically deserted after Russia, his sole international interlocutor joined the rest of the G8 nations in declaring the Libyan leader had lost all legitimacy and had to go.

But continuing differences between Russia and the west prevented agreement on how to pressurise the Syrian regime to end its oppression; a planned reference to take the issue to the UN security council was removed from the G8 communique.

On Libya, David Cameron claimed there would be no attempt to reach a compromise deal, saying the only message to the Libyan leader was that he had to give up power. Cameron, who held a council of war with Barack Obama and Nicolas Sarkozy on Thursday night, claimed the war against Gaddafi was entering a second phase and the pressure on the regime was beginning to tell.

There had been suggestions that the Russians would act as some kind of mediator in trying to secure a peace deal with Gaddafi, but Cameron said the Russian president, Dmitry Medvedev, had not made this suggestion in the discussions he had had with them.

Cameron said: "The most important thing is to send the same message down the pipe when one of these offers appears and the message is that Gaddafi has to go. All sorts of things can happen after that. All offers of mediation should be met with that pretty clear response."

He said the Tripoli regime was beginning to feel the heat, revealing: "There is a whole string of contacts taking place, of phone calls and faxes coming out saying 'how do we get out of this, what do we about this?' to which I say there is one clear response: Gaddafi has to go."

Sarkozy revealed he had been discussing a joint visit with Cameron to the rebel stronghold of Benghazi, but Cameron's aides played down the prospect of an imminent trip.

Sarkozy also highlighted the terms of the communique, saying: "There is unanimous support for this objective and the terms used against Gaddafi are particularly clear and hard and accepted by all the G8 countries including Russia."

In unusually simple language for a G8 communique, the leaders of the industrialised west said: "Gaddafi and the Libyan government have failed to fulfil their responsibility to protect the Libyan population and have lost all legitimacy. He has no future in a free, democratic Libya. He must go.

"We welcome the work of the international criminal court in investigating crimes in Libya and note the chief prosecutor's request on 16 May for three arrest warrants." The Russians said they would send a delegation to Benghazi, but would not accept Gaddafi into exile.

Cameron conceded the communique was less clear on Syria, admitting that the Arab world was divided as to whether President Bashar al-Assad might yet take the fork in the road towards reconciliation.

Sarkozy was more blunt: "The situation is perfectly unacceptable and the attitude of the powers in the country is shocking. We have done everything we can to bring Syria into the international community. We have tried to help, to advise, to understand … sadly the leaders are going firmly backwards and we have withdrawn our confidence and criticised what has to be criticised."

The shift in the communique language to a vaguer threat of "further measures" appeared to be driven by Russia, which has a security council veto and has been upset by the way in which the west has interpreted its right to bomb Gaddafi following an earlier UN resolution giving Nato all necessary powers to protect civilians.

"There are no grounds to consider this issue [Syria] in the UN security council," Russia's deputy foreign minister, Sergei Ryabkov, told reporters. He said a draft resolution circulated to the 15-nation council on Wednesday by Britain, France, Germany and Portugal was "untimely and damaging", adding: "We will not even read the text." The draft resolution could also face a Chinese veto.

The language on Libya by contrast at the G8 will be seen as a victory for Sarkozy, suggesting he managed to persuade a reluctant Russian delegation to bury their doubts about the scale of the military offensive, including the decision by the French and British to provide ground attack helicopters for use by Nato.

In other parts of the communique the language on Libya is less robust, stating: "We are committed to supporting a political transition that reflects the will of the Libyan people. We recall our strong commitment to the sovereignty, independence, territorial integrity and national unity of Libya."

Elsewhere in the communique, the leaders of the biggest industrialised countries also claim "the world economy is recovering", even if more needs to be done to reduce global imbalances and deficits.