Tbilisi yesterday did not feel like a city at war. Despite the Russian tanks just outside the city on the main road to Gori, people went about their Saturday business.

The city has the trappings of a vibrant western economy. Billboards advertised designer products. The one-time Marxism-Leninism Institute is now a five-star hotel. Only the flags at half-mast indicated that all was not well.

As I arrived in Georgia yesterday to see President Saakashvili, I expected a city under siege. Instead I found a people displaying strength in the face of a bully. Whatever the criticisms of Georgia’s actions, there can be no justification for Russia’s use of massive and overwhelming military force against a neighbour and a democracy. Russia’s actions have laid down a formidable challenge to the West and to the institutions of the modern world. The question is simple: will the West step up to the plate?

With each day that has passed has come a growing recognition of what Russia’s invasion means: for Georgia, for Russia, for the region and for the whole world. And with that recognition has come an understanding of the need for a firm and urgent response.

What should that mean? First, speaking up clearly and bluntly about what has happened. This is not a time for diplomatic opaqueness. It is a time to distinguish unambiguously between right and wrong. It is a time for democracies to stand together. It is a time for members of our parliament – the seat of one of the world’s oldest democracies – to speak up for one of the world’s newest. Today, in Georgia’s hour of need, this instinct unites government and opposition.

Second, we need urgent diplomatic efforts, in which Britain must play a leading role. Russian forces must leave Georgia right away as they are required to do under the ceasefire agreement both sides have signed.

Third, Russia must pay a price. Russia wants international recognition and respect. We must make clear that the path it has chosen leads to isolation and contempt. We should suspend Russia from the G8 and defer negotiations on a partnership with the European Union.

Russia’s elite value their ties to Europe - their shopping and their luxury weekends. We should look at the visa regime for Russian citizens. Russian armies can’t march into other countries while Russian shoppers carry on marching into Selfridges. And we must make clear that Georgia’s aspiration to be a member of Nato remains alive and well. The alliance should offer Georgia a clear pathway to membership.

Fourth, there are mounting concerns about the activities of the militias and irregular forces. There are anxieties about the danger of Balkan-style atrocities perpetuated by para-military forces while regular forces turn a blind eye. Such allegations must be fully investigated and those responsible held to account.

If the world stands by as Georgia falls under the Russian boot, a vibrant democracy will have been extinguished. Russia is trying to frighten neighbours, making it clear the ex-Soviet or Warsaw Pact states enjoy only a limited sovereignty. Today it is Georgia. Tomorrow will it be Ukraine? Or the Baltic states?

So Nato, the EU and the western democracies must act. When I was in Tbilisi, reports came in that a key railway bridge had been blown up. We must work to rebuild what Russia has destroyed, sending a clear message that we stand by our friends. If we fail to do so, we will have suffered a disastrous blow to our credibility.

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