Lewis Hamilton
Hamilton and Scherzinger have ended their four-year relationship. REUTERS

Lewis Hamilton's poor F1 season took a turn for the worse Thursday, after reports suggested he has split with long-term girlfriend Nicole Scherzinger.

Pussycat Doll and U.S. "X Factor" judge Scherzinger met Hamilton in Munich in 2007 but they reached an "amicable" decision to end their four-year relationship over the weekend citing their "unworkable schedules."

After a torrid F1 season, Hamilton finished second in last weekend's Korean Grand Prix but his race schedule, combined with Scherzinger's own work commitments, have finally put paid to their relationship.

"Lewis and Nicole have been having problems for the past six weeks," a source close to the couple told the Mirror.

"Increasingly hectic schedules this year have meant limited face-to-face time. They've probably spent more time on the phone or on Skype than they have in person.

"[They] have tried to make it work but realised it's just not happening so have called it a day once and for all."