Labour MP Ben Bradshaw has told the House of Commons it is "highly probable" that Russia secretly intervened in the EU referendum in order to influence the result.
The MP made the comment during his speech on the crisis in Syria, warning that the growing influence of Russia was affecting countries across the world and saying that where the Kremlin could not deploy its military it was turning to online attacks through disinformation and hacking.
However, Bradshaw admitted he did not "yet" have the evidence to back up his claim about Russian influence in the EU referendum.
"I don't think we have even begun to wake up to what Russia is doing when it comes to cyber warfare," the MP said during the parliamentary debate on the crisis in Aleppo.
"Not only their interference, now proven, in the American presidential campaign, probably in our referendum last year – we don't have the evidence for that yet but I think it's highly probable – certainly in the French presidential election they will be involved, and there are already serious concerns in the German secret service.
"We've got to wake up to this! When are we going to wake up to this?"
There have previously been claims of Russian influence in British politics but little has been offered in the way of concrete evidence. Last week the head of MI6 warned of the threat to democracy posed by online cyber warfare from countries such as Russia.
Bradshaw said Russia's president, Vladimir Putin, was turning to online attacks when military means did not work: "When will we understand that dictators like Assad and Putin only respect strength and the credible threat of – or the use of – force?
"When will we realise that Russia's strategy is to weaken and divide the free world and that driving the biggest refugee flows into Europe since World War II is a deliberate part of that plan? When will we admit that what Putin can't achieve militarily he is already achieving using cyber and propaganda warfare?"
He said the situation in Aleppo, where Syrian government troops backed by Russia are recapturing the city from rebels amid claims of civilian suffering on a mass scale, was a "tragedy" that shamed the world.
"Why do we constantly forget the lessons of appeasement, whether from the 1930s or more recently from the Balkans?" he asked.
"It shames the democratic world, the United States, and the United Nations. If we do nothing about this, it is the end of the rules-based global order that we thought we had achieved after Srebrenica."