The Labour Party has said that it has experienced a “sophisticated and large scale cyber attack” on its digital platforms.
A Labour spokeswoman said the cyber attack had "failed" because of the party's "robust security systems" and that they were confident that no data breach occurred.
Some campaigning activities were temporarily slowed, but the systems were back up to speed this morning.
The party has not specified which of its digital platforms were targeted, but its social media accounts and main website are functioning as normal.
The spokeswoman said they had reported the matter to the National Cyber Security Centre (NCSC).
Labour sources would not reveal further details of the attack or who they thought might be responsible.
In a statement, the party said: "We have experienced a sophisticated and large scale cyber attack on Labour digital platforms," the spokeswoman said.
"We took swift action and these attempts failed due to our robust security systems. The integrity of all our platforms was maintained and we are confident that no data breach occurred."
The last general election in 2017 was disrupted by the worldwide WannaCry attack, which hit hundreds of NHS trusts and GP practices, leading to thousands of appointments and operations being cancelled.
The NCSC subsequently attributed the attack to a shadowy North Korean crime organisation known as the Lazarus group.