Former England captain Andrew Strauss has apologised after he was caught on microphone making derogatory remarks about ex-team mate Kevin Pietersen during an MCC v Rest of the World exhibition match at Lord's.

Strauss was heard by viewers who were watching the coverage on Fox Sports in Australia but the comments were not broadcast on British television.

"I apologise unreservedly, particularly to Kevin Pietersen," Strauss said as his error became public knowledge. "I am mortified and profusely sorry."

He reportedly made the remarks - calling Pietersen a c*** - while speaking to fellow commentator Nick Knight, forcing Sky Sports television to issue an apology.

"Earlier comments were made during a break of play which were heard overseas. We apologise for the language used," the broadcaster said on its Twitter account.

The South African-born Pietersen, who was sacked by England after the 5-0 Ashes defeat in Australia earlier this year, was dropped for a Test against South Africa in 2012 after sending provocative texts about Strauss to the opposition.

The match at Lord's is being held to celebrate the bicentenary of the famous ground.