LONDON (REUTERS) - A bemused Jose Mourinho described Chelsea's performance as unacceptable and a disgrace after the Premier League leaders slumped to a 4-2 home defeat against third-tier Bradford City in the FA Cup fourth round on Saturday.

It was an old-fashioned Cup tie, full of noise, tension, rip-roaring goals and a thrilling comeback victory for the brave underdogs on a chilly afternoon in west London.

Mourinho, twice a Champions League winner, who has led teams to titles in his native Portugal, Italy and Spain as well as at Chelsea, said the defeat was one of the worst of his career.

"I feel ashamed and I feel the players should feel the same as I feel," he told reporters.

It was the first time a Mourinho Chelsea side had lost to lower league opposition during his two wpells in England.

"It's a disgrace - a sporting disgrace obviously but still a disgrace."

The Chelsea manager said team rotation, after he rested several players, could not be used as an excuse for the rout.

"This happens to every team from time to time, but for me it's the first time - it's unacceptable to lose against a team form a lower league."

Chelsea last lost to lower league opposition in 2008 under Avram Grant when they were beaten by Barnsley - who are also from Yorkshire.

"We are not speaking about a team of kids so I think the selection was more than good enough and obviously the word disgrace is the right word," Mourinho said.

He added that not one of the Bradford players "with respect" would make it into a Chelsea side.

The hosts looked to be coasting after goals from England centre back Gary Cahill and Brazil midfielder Ramires.

But a thundering strike from Jon Stead just before halftime rocked Mourinho's side and when former Chelsea man Filipe Morais equalised in the 75th minute, the League One visitors were brimming with new-found confidence.

FINE GOALS

Chelsea's defence was susceptible as they threw men forward to find a winner and fine goals on the break from Bradford's Andy Halliday and substitute Mark Yeates sent the visiting fans, packing Stamford Bridge's Shed End, into delirium.

"I could find in my bad feeling with the game and with the result... space to feel happy for them (Bradford)," Mourinho told reporters.

"On one side this is the beauty of the FA cup the beauty of football.

"You should be very critical of Chelsea, the manager and the players. But the others (Bradford) deserve that we focus not just on the negative but also on them after such an impressive result."

Bradford manager Phil Parkinson said the victory was only just sinking in.

"It will be remembered in Bradford for a long time," he said.

"I told the players before the game... we've got to send our supporters back up the motorway proud of the team."

Parkinson said he rebuffed Mourinho's attempts to shake hands in the dugout with the match still in progress due to the seven minutes added on by referee Andre Marriner. "With three minutes to go against Chelsea, anything could happen," he said.

Chelsea have two days to lick their wounds before hosting Liverpool in the League Cup semi-final, after a 1-1 draws at Anfield in the first leg.

Next Sunday they have a top-of-the-table Premier League clash at home to Manchester City.