Video - The use of a Russian nerve agent is part of a clear pattern of aggression from Russia that threatens the global rule of law, High Commissioner to New Zealand Laura Clarke says.
British Prime Minister Theresa May has said 23 Russian diplomats are "undeclared intelligence officers" and they have been given a week to leave the country after Russia failed to explain the use of a nerve agent against an ex-spy.
Russia denies being involved in the attempted murder of Sergei Skripal.
It is the largest mass expulsion since 31 were ordered out in 1985 after double agent Oleg Gordievsky defected.
Former spy Mr Skripal, 66, and his daughter, Yulia Skripal, 33, remain critically ill in hospital after being found slumped on a bench on 4 March.
Ms Clarke said the British government was very clear in its assessment that the Novichok nerve agent had come from Russia.
"That means that either it is a direct act by the Russia government or Russia has lost control over its stock of the agent," she said.
"Also it fits very much into a pattern of Russian aggressive behaviour: the illegal annexation of Crimea, violating European airspace, hostile cyber attacks, of course the Litvinenko murder with polonium ... to support of Assad's regime in Syria where chemical weapons have been used."
She said it was an undermining of the international rules system.
"This isn't just a violation of chemical weapons convention, it's a breach of international law, and also it's a violation of the rules-based order, the values that we all work to in order that the world functions as a number of states working together.
"New Zealand more than any other country needs the rules-based order to work.
"Although that sounds like a dry term if you're a small outward-looking trading nation like New Zealand, you need the laws to work. You need international law to work, you need all these things to function, and what Russia's doing is undermining those laws.
Asked about accusations against Russia over MH17 and meddling in the US election, she said she didn't want to go through a specific list of Russia's aggression, but there was an overall pattern of aggressive behaviour.
Russian Ambassador on nerve agent accusations
Russia's ambassador to New Zealand, Valery Tereshchenko, said the Salisbury attack was a well-planned provocation aimed at fanning an anti-Russian campaign.
Speaking to Morning Report via an interpreter, Mr Tereshchenko said there was no motive for Russia to carry out the attack which has also injured one of their own citizens.
"According to the official statement of the Russian government Russia has nothing to do with what happened to Mr Skripal and his daughter Yulia," he said.
"In addition to that we asked the British partners to allow us to make a joint investigation or an additional investigation into what had happened before, into what nerve agents in particular were used to poison Mr Skripal and his daughter Yulia.
"But the British partners refused to do that."
He said he would like to underline that Yulia is a Russian citizen.
He also implied it was suspicious how quickly Britain had analysed the nerve agent and come to the conclusions it had.
"It is surprising that the British side has made conclusions so fast and they stated clearly that the trails lead to Russia. People who can think logically can ask why Russia would need this right now."
He said that according to the information available, the USSR used to produce the Novichok nerve agent, but in 1992 an American group of specialists dealt with the elimination of the laboratory and the chemicals.
Mr Tereshchenko said he could not say for sure where the nerve agent, if that was what it was, was brought from.
"But a specialist - an expert, a chemist - who devel that kind of agent in 1996 ran away from the territory of the Russian Federation and moved to the United States.
"It was Mr Mirzayanov, he allegedly developed that military grade agent and probably he knows the formula. It can be that the American side could have brought that kind of agent on the territory of the country."
Vil Mirzayanov, 83, told Reuters from his home in Princeton, New Jersey yesterday he spent years testing and improving Novichok, and that he had no doubt Russian President Vladimir Putin was responsible for the Salisbury attack.
He said Russia maintains tight control over its Novichok stockpile and that the agent is too complicated for a non-state actor to have weaponised.
"Novichok was invented and studied and experimented and many tons were produced only in Russia. Nobody knew in this world," he said.
After moving to the US, Mr Mirzayanov published a book in 2008 exposing what he knew about Russia's covert Cold War chemical weapons program.
High Commissioner on trade deals with NZ
Ms Clarke said the United Kingdom very much welcomed the statements by deputy Prime Minister Winston Peters' and trade minister David Parker about the use of the nerve agent.
"We're very pleased that New Zealand's been very clear in its statement that, as I quote, it 'shares the UK's outrage'. New Zealand is of course a very close partner of the UK."
New Zealand's pursuit of a free trade agreement with Russia was not something the UK had a say in, and Ms Clarke would not say whether it would affect the likelihood of similar agreements with the European Union, or Britain once it left the union.
"Who New Zealand does fair trade agreements with is a matter for New Zealand ... it wasn't discussed in the conversation yesterday but we have various channels of communication.
However, she said New Zealand signing any future free trade agreement with Russia could possibly create an issue of "compatibility" with similar agreements signed with the EU and, after Brexit, the UK.
New Zealand's free trade agreement talks with Russia were suspended in 2014, following Russia's military intervention into Ukraine.
She said New Zealand's decision about who it conducts free trade agreements with is a domestic one, but it does not occur in a vacuum, as a range of international factors are discussed.
"But of course, these discussions between the UK and New Zealand, between the EU and New Zealand - different factors are always discussed and that's probably as far as I can go for now.
"Some things we disclose and some things we don't."
She did say the EU had sanctions against Russia in place over its annexation of Crimea, and that the UK was supportive of New Zealand free trade agreements with the EU and the UK.