The UK will “respond appropriately and robustly” if the Russian state is found to have been involved in poisoning the former Russian double agent Sergei Skripal and his daughter Yulia in Salisbury on Sunday, Boris Johnson has said, including reconsidering its participation in the World Cup.

The foreign secretary said it was “very difficult to see how UK representation at that event could go ahead in the normal way” if Russian state involvement was proved, though a Foreign Office source said that was not a reference to the England team’s participation.

Johnson said he was not yet pointing fingers at the Kremlin, but adding that there were “echoes of the death of Alexander Litvinenko in 2006”.

“I say to governments around the world that no attempt to take innocent life on UK soil will go unsanctioned or unpunished,” Johnson said, later calling the Russian state “in many respects a malign and disruptive force”.

“It is too early to speculate as to the precise nature of the crime or attempted crime that has taken place in Salisbury,” he said. “But I know members will have their suspicions. If those suspicions prove to be well-founded then this government will take whatever measures we deem necessary to protect the lives of the people in this country, our values and our freedoms.”

Johnson said the UK may “continue to pay a price” for continued sanctions against Russia but said he hoped MPs would support the government’s approach, which had “inflicted considerable damage on the Russian economy”.

Play Video 2:03 Who is the Salisbury spy Sergei Skripal? – video explainer

The UK government might decide it was not appropriate for representatives to attend the World Cup, he said. “I think if things turns out to be as many members of the house may suspect that they are, I think we will have to have a serious conversation about our engagement with Russia,” Johnson said.

“And for my own part I think it will be very difficult to see, thinking ahead to the World Cup this July, I think it would be very difficult to see how UK representation at that event could go ahead in the normal way. We would certainly have to consider that.”

A Foreign Office source said Johnson was referring to the attendance of officials and dignitaries at the tournament, an example of the “soft power” as well as sanctions, which was available for the UK to show its displeasure.

The foreign secretary’s response came after an urgent question from the Conservative MP Tom Tugendhat, the chair of the foreign affairs select committee, who said the attack may be “a form of soft war that Russian is now conducting against the west”.

“It is quite clear we are seeing a pattern of Russian behaviour,” Tugendhat said. “This is what the KGB would call demoralise, destabilise, bring to crisis and then normalise. This requires a whole of government response and his department [FCO] is best placed to lead that response.”

Johnson said the UK was “in the lead across the world trying to counter Russian activity” including tackling propaganda.

“I have to say to the house it is sometimes difficult, given the strong economic pressures exerted on other European economies,” he said. “But we do get our points across and there has been no wavering in the sanctions regime.”

Johnson said the UK government increasingly viewed Russian cyber-attacks as “acts of war” against Britain. “That means that we need to elaborate a new doctrine of response and a new doctrine of deterrence as well, and we certainly are. That is one of the conclusions that we took in the NSC [national security council] a few months ago,” he said.

The shadow foreign secretary, Emily Thornberry, said MPs were extremely concerned about the incident in Salisbury, praising the emergency services’ bravery given the risks and the history of other poisonings.

Police were continuing on Tuesday to try to establish the substance that Skripal, 66, and his daughter were exposed to in Salisbury at the weekend. Both remained in critical condition and in intensive care.

The UK’s leading counter-terrorism officer, the Metropolitan police assistant commissioner Mark Rowley, said on Tuesday that his specialists were supporting the investigation. “Clearly it’s a very unusual case and the critical thing is to get to the bottom of what has caused this incident as quickly as possible,” he said.

Skripal was one of four Russians exchanged for 10 deep cover “sleeper” agents planted by Moscow in the US in 2010.