Channel 4 attempted to cool an escalating row over alleged bullying of actress Shilpa Shetty on Celebrity Big Brother, saying there was no clear evidence of racism.

As the number of complaints to the media regulator topped 19,000 and police probed e-mail threats against housemates, the broadcaster said Shetty had not spoken out about any racism.

"There has been no overt racial abuse or racist behaviour directed against Shilpa. However, there has undoubtedly been a cultural and class clash between her and three of the British females," Channel 4 said in a statement on Wednesday.

Singer Jo O'Meara, reality TV star Jade Goody and model Danielle Lloyd face claims that they have ganged together to bully Shetty.

Media watchdog, Ofcom said 19,300 viewers have complained about her treatment.

Questions were also asked in the House of Commons, forcing Prime Minister Tony Blair to express his opposition to "racism in all its forms". India, too, has taken up the issue with the British government after a series of protests.

After the controversy the highlights of the show reportedly drew the third biggest ratings of the series as the real-life drama made headlines in British and Indian newspapers.

Police in Hertfordshire said two e-mailed threats had been sent to the show's broadcaster Channel 4.

"(They) contain unspecified threats against a number of the housemates. Police are currently looking in to the e-mails," a spokesman said.

Detectives also received a telephone call complaining about ''alleged racist behaviour'' on the programme, he said. The caller was referred to the media watchdog Ofcom.