Bayern Munich comfortably beat 10-man RB Leipzig 3-0 to move three points clear of their title rivals and ensure they will spend Christmas on top of the Bundesliga.
The two sides came into their first competitive meeting with only goal difference separating them, but the champions made a huge statement in emphatically winning their fifth consecutive league game.
Robert Lewandowski's penalty – his 12th league goal of the season – added to Leipzig's misery before the break and Bayern cruised to victory from then on, with substitute Franck Ribery hitting the crossbar.
Leipzig had won nine of their previous 10 league games having impressed hugely after promotion, but will now have to reflect on their morale-sapping defeat during the Bundesliga's one-month mid-season break.
The opening goal arrived in the 17th minute when Lahm's cross from the right led to Lewandowski's effort striking the post, with Thiago applying a first-time finish on the rebound.
Bayern almost struck again a few moments later, Douglas Costa hitting the post having been found by Lewandowski.
Naby Keita lost possession in a dangerous area for Leipzig, which allowed Lewandowski and Thiago to combine before the ex-Barcelona midfielder fed Alonso to send a side-footed finish into the bottom-left corner.
Willi Orban had a header brilliantly saved by Neuer as the visitors searched for a way back into the game, but their hopes took another hit in the 30th minute.
Forsberg put in a nasty challenge from behind on Lahm as the Bayern captain attempted to launch a counter-attack and referee Felix Zwayer deemed it was worthy of a red card – but only after Bayern protests and discussion with his assistant.
Bayern made it three in the last minute of the first half after Costa, who was fortunate not to be flagged offside, raced on to a high ball and was brought down by goalkeeper Peter Gulacsi just inside the area.
Lewandowski calmly sent Gulacsi the wrong way from the resulting spot-kick.
Ribery came on for Arjen Robben at half-time and Bayern continued to press, Gulacsi having to rush out quickly to deny Lewandowski.
Marcel Sabitzer had an a shot deflected wide, but Bayern were looking more likely to strike again, with Gulacsi helping Lewandowski's chip over the bar after good play from Ribery.
Ribery saw a late effort bounce off the crossbar after being found by Alonso, with Leipzig barely threatening in the closing stages to leave Carlo Ancelotti's men celebrating a third straight clean sheet and a clear advantage at the top of the table.