LISBON, March 27 (Xinhua) -- Portugal's Minister for Foreign Affairs Augusto Santos Silva on Tuesday defended the government's decision not to expel Russian diplomats.

"At every moment we take whatever measure shows itself to best comply with Portugal's national interests, Europe's interests and NATO's interests," Santos Silva told Portuguese Lusa News Agency.

Some 25 countries, including 16 members of the European Union (EU), expelled Russian diplomats on Tuesday, in a show of solidarity with the British government.

Sergei Skripal, a former Russian spy, was poisoned in Salisbury, England, on March 4. The British government blames Moscow.

Portugal issued a statement saying: "Portugal immediately condemned the attack in Salisbury and vehemently expressed its solidarity with the United Kingdom."

But the statement added, "Portugal believes collaboration through the framework of the EU is the most efficient method for responding to the gravity of the current situation."

As things stand, Portugal lines up alongside Austria and Greece as EU member countries that have not expelled Russian diplomats, though all have condemned the poisoning.

Santos Silva argued that Portugal's Socialist Party (PS) government had thus acted "without haste, with autonomy, with prudence, and with firmness too."

He had the backing of Catarina Martins, leader of the Left Bloc (BE), an informal coalition partner of the PS.

"The poisoning of a spy as a weapon of external politics must be vehemently condemned," said Martins, but she disapproved of Europe's will to escalate tensions. "It seems prudent to us that the Portuguese government did not wish to take part in this escalation and we hope it maintains this position."

Rubina Berardo, vice-president of the opposition Social Democratic Party (PSD), was also cautious in offering her party's response.

"The PSD is a responsible party and we await clarification on the part of the government regarding the decision not to expel Russian diplomats," she told TSF radio.