Labour leader Sir Keir Starmer visited Carlisle after winning a majority in the new Cumberland Council in the local elections.
The party secured 30 out of 46 seats, with the Conservatives getting just seven.
He said: "This is a real turning point for the Labour party, we've shown that we can win, we can win in the north, in Cumberland with key constituencies sitting behind these wins in the north, Rossendale just come in.
"We've shown also we can win in the south, in Southampton we took Southampton overnight and then of course historic wins in London. Seats that it was said Labour could never gain.
"So we've got the wind in our sails, we're on the march and we've got the next General Election very firmly in our sights."
The new unitary authority contains the districts of Carlisle, Allerdale and Copeland.
It will formally take over responsibility for all services in April 2023, when the existing county and district councils will be abolished.