The 'Toxic' singer is said to be 'distraught' after learning Jason Trawick had been flirting with two women at Los Angeles' bar Roger Room and is now refusing to take his calls.

Ella Davis, a reveller at the bar, told the Daily Mirror newspaper: "Jason left the bar with two bottles of water - and a stunning blonde who looked like Britney.

'He had his arms around her and they looked very much like they were together for the night."

Friends of Jason – who has proposed to Britney a number of times – have defended him, insisting his behaviour is out of character.

A source added: 'Jason's a great guy and super loyal. This behaviour is really out of character. But Los Angeles is a small town and word soon got back to Britney he'd had a wild one.

'When she heard he'd been caught cosying up two girls in The Roger Room, it was the last straw. Jason's really not like this and quickly tried to calm Britney down and rectify the situation. He explained the girls were just friends and there was nothing in it but they still had a massive row.

'Everyone is assuming it's over – for the time being anyway.'

After the argument Britney called her mother who has flown in from Louisiana to comfort her.

Britney - who has two sons with ex-husband Kevin Federline - and agent Jason started dating last March. They split briefly in August, but soon reconciled.